_(value) → {Object}

new _(value) → {Object}

Creates a lodash object which wraps value to enable implicit method
chain sequences. Methods that operate on and return arrays, collections,
and functions can be chained together. Methods that retrieve a single value
or may return a primitive value will automatically end the chain sequence
and return the unwrapped value. Otherwise, the value must be unwrapped
with _#value.

Explicit chain sequences, which must be unwrapped with _#value, may be
enabled using _.chain.

The execution of chained methods is lazy, that is, it's deferred until
_#value is implicitly or explicitly called.

Lazy evaluation allows several methods to support shortcut fusion.
Shortcut fusion is an optimization to merge iteratee calls; this avoids
the creation of intermediate arrays and can greatly reduce the number of
iteratee executions. Sections of a chain sequence qualify for shortcut
fusion if the section is applied to an array and iteratees accept only
one argument. The heuristic for whether a section qualifies for shortcut
fusion is subject to change.

Chaining is supported in custom builds as long as the _#value method is
directly or indirectly included in the build.

In addition to lodash methods, wrappers have Array and String methods.

The wrapper Array methods are:
concat, join, pop, push, shift, sort, splice, and unshift

The wrapper String methods are:
replace and split

The wrapper methods that support shortcut fusion are:
at, compact, drop, dropRight, dropWhile, filter, find,
findLast, head, initial, last, map, reject, reverse, slice,
tail, take, takeRight, takeRightWhile, takeWhile, and toArray

The chainable wrapper methods are:
after, ary, assign, assignIn, assignInWith, assignWith, at,
before, bind, bindAll, bindKey, castArray, chain, chunk,
commit, compact, concat, conforms, constant, countBy, create,
curry, debounce, defaults, defaultsDeep, defer, delay,
difference, differenceBy, differenceWith, drop, dropRight,
dropRightWhile, dropWhile, extend, extendWith, fill, filter,
flatMap, flatMapDeep, flatMapDepth, flatten, flattenDeep,
flattenDepth, flip, flow, flowRight, fromPairs, functions,
functionsIn, groupBy, initial, intersection, intersectionBy,
intersectionWith, invert, invertBy, invokeMap, iteratee, keyBy,
keys, keysIn, map, mapKeys, mapValues, matches, matchesProperty,
memoize, merge, mergeWith, method, methodOf, mixin, negate,
nthArg, omit, omitBy, once, orderBy, over, overArgs,
overEvery, overSome, partial, partialRight, partition, pick,
pickBy, plant, property, propertyOf, pull, pullAll, pullAllBy,
pullAllWith, pullAt, push, range, rangeRight, rearg, reject,
remove, rest, reverse, sampleSize, set, setWith, shuffle,
slice, sort, sortBy, splice, spread, tail, take, takeRight,
takeRightWhile, takeWhile, tap, throttle, thru, toArray,
toPairs, toPairsIn, toPath, toPlainObject, transform, unary,
union, unionBy, unionWith, uniq, uniqBy, uniqWith, unset,
unshift, unzip, unzipWith, update, updateWith, values,
valuesIn, without, wrap, xor, xorBy, xorWith, zip,
zipObject, zipObjectDeep, and zipWith

The wrapper methods that are not chainable by default are:
add, attempt, camelCase, capitalize, ceil, clamp, clone,
cloneDeep, cloneDeepWith, cloneWith, conformsTo, deburr,
defaultTo, divide, each, eachRight, endsWith, eq, escape,
escapeRegExp, every, find, findIndex, findKey, findLast,
findLastIndex, findLastKey, first, floor, forEach, forEachRight,
forIn, forInRight, forOwn, forOwnRight, get, gt, gte, has,
hasIn, head, identity, includes, indexOf, inRange, invoke,
isArguments, isArray, isArrayBuffer, isArrayLike, isArrayLikeObject,
isBoolean, isBuffer, isDate, isElement, isEmpty, isEqual,
isEqualWith, isError, isFinite, isFunction, isInteger, isLength,
isMap, isMatch, isMatchWith, isNaN, isNative, isNil, isNull,
isNumber, isObject, isObjectLike, isPlainObject, isRegExp,
isSafeInteger, isSet, isString, isUndefined, isTypedArray,
isWeakMap, isWeakSet, join, kebabCase, last, lastIndexOf,
lowerCase, lowerFirst, lt, lte, max, maxBy, mean, meanBy,
min, minBy, multiply, noConflict, noop, now, nth, pad,
padEnd, padStart, parseInt, pop, random, reduce, reduceRight,
repeat, result, round, runInContext, sample, shift, size,
snakeCase, some, sortedIndex, sortedIndexBy, sortedLastIndex,
sortedLastIndexBy, startCase, startsWith, stubArray, stubFalse,
stubObject, stubString, stubTrue, subtract, sum, sumBy,
template, times, toFinite, toInteger, toJSON, toLength,
toLower, toNumber, toSafeInteger, toString, toUpper, trim,
trimEnd, trimStart, truncate, unescape, uniqueId, upperCase,
upperFirst, value, and words

Parameters:
Name Type Description
value *

The value to wrap in a lodash instance.

Returns:
Object -

Returns the new lodash wrapper instance.

Example
function square(n) {
  return n * n;
}

var wrapped = _([1, 2, 3]);

// Returns an unwrapped value.
wrapped.reduce(_.add);
// => 6

// Returns a wrapped value.
var squares = wrapped.map(square);

_.isArray(squares);
// => false

_.isArray(squares.value());
// => true

Members

static add

Adds two numbers.

Since:
  • 3.4.0
Example
_.add(6, 4);
// => 10

static assign

Assigns own enumerable string keyed properties of source objects to the
destination object. Source objects are applied from left to right.
Subsequent sources overwrite property assignments of previous sources.

Note: This method mutates object and is loosely based on
Object.assign.

Since:
  • 0.10.0
See:
  • _.assignIn
Example
function Foo() {
  this.a = 1;
}

function Bar() {
  this.c = 3;
}

Foo.prototype.b = 2;
Bar.prototype.d = 4;

_.assign({ 'a': 0 }, new Foo, new Bar);
// => { 'a': 1, 'c': 3 }

static assignWith

This method is like _.assign except that it accepts customizer
which is invoked to produce the assigned values. If customizer returns
undefined, assignment is handled by the method instead. The customizer
is invoked with five arguments: (objValue, srcValue, key, object, source).

Note: This method mutates object.

Since:
  • 4.0.0
See:
  • _.assignInWith
Example
function customizer(objValue, srcValue) {
  return _.isUndefined(objValue) ? srcValue : objValue;
}

var defaults = _.partialRight(_.assignWith, customizer);

defaults({ 'a': 1 }, { 'b': 2 }, { 'a': 3 });
// => { 'a': 1, 'b': 2 }

static at

This method is the wrapper version of _.at.

Since:
  • 1.0.0
Example
var object = { 'a': [{ 'b': { 'c': 3 } }, 4] };

_(object).at(['a[0].b.c', 'a[1]']).value();
// => [3, 4]

static at

Creates an array of values corresponding to paths of object.

Since:
  • 1.0.0
Example
var object = { 'a': [{ 'b': { 'c': 3 } }, 4] };

_.at(object, ['a[0].b.c', 'a[1]']);
// => [3, 4]

static attempt

Attempts to invoke func, returning either the result or the caught error
object. Any additional arguments are provided to func when it's invoked.

Since:
  • 3.0.0
Example
// Avoid throwing errors for invalid selectors.
var elements = _.attempt(function(selector) {
  return document.querySelectorAll(selector);
}, '>_>');

if (_.isError(elements)) {
  elements = [];
}

static bind

Creates a function that invokes func with the this binding of thisArg
and partials prepended to the arguments it receives.

The _.bind.placeholder value, which defaults to _ in monolithic builds,
may be used as a placeholder for partially applied arguments.

Note: Unlike native Function#bind, this method doesn't set the "length"
property of bound functions.

Since:
  • 0.1.0
Example
function greet(greeting, punctuation) {
  return greeting + ' ' + this.user + punctuation;
}

var object = { 'user': 'fred' };

var bound = _.bind(greet, object, 'hi');
bound('!');
// => 'hi fred!'

// Bound with placeholders.
var bound = _.bind(greet, object, _, '!');
bound('hi');
// => 'hi fred!'

static bindAll

Binds methods of an object to the object itself, overwriting the existing
method.

Note: This method doesn't set the "length" property of bound functions.

Since:
  • 0.1.0
Example
var view = {
  'label': 'docs',
  'click': function() {
    console.log('clicked ' + this.label);
  }
};

_.bindAll(view, ['click']);
jQuery(element).on('click', view.click);
// => Logs 'clicked docs' when clicked.

static bindKey

Creates a function that invokes the method at object[key] with partials
prepended to the arguments it receives.

This method differs from _.bind by allowing bound functions to reference
methods that may be redefined or don't yet exist. See
Peter Michaux's article
for more details.

The _.bindKey.placeholder value, which defaults to _ in monolithic
builds, may be used as a placeholder for partially applied arguments.

Since:
  • 0.10.0
Example
var object = {
  'user': 'fred',
  'greet': function(greeting, punctuation) {
    return greeting + ' ' + this.user + punctuation;
  }
};

var bound = _.bindKey(object, 'greet', 'hi');
bound('!');
// => 'hi fred!'

object.greet = function(greeting, punctuation) {
  return greeting + 'ya ' + this.user + punctuation;
};

bound('!');
// => 'hiya fred!'

// Bound with placeholders.
var bound = _.bindKey(object, 'greet', _, '!');
bound('hi');
// => 'hiya fred!'

static camelCase

Converts string to camel case.

Since:
  • 3.0.0
Example
_.camelCase('Foo Bar');
// => 'fooBar'

_.camelCase('--foo-bar--');
// => 'fooBar'

_.camelCase('__FOO_BAR__');
// => 'fooBar'

static ceil

Computes number rounded up to precision.

Since:
  • 3.10.0
Example
_.ceil(4.006);
// => 5

_.ceil(6.004, 2);
// => 6.01

_.ceil(6040, -2);
// => 6100

static chain

Creates a lodash wrapper instance with explicit method chain sequences enabled.

Since:
  • 0.1.0
Example
var users = [
  { 'user': 'barney', 'age': 36 },
  { 'user': 'fred',   'age': 40 }
];

// A sequence without explicit chaining.
_(users).head();
// => { 'user': 'barney', 'age': 36 }

// A sequence with explicit chaining.
_(users)
  .chain()
  .head()
  .pick('user')
  .value();
// => { 'user': 'barney' }

static commit

Executes the chain sequence and returns the wrapped result.

Since:
  • 3.2.0
Example
var array = [1, 2];
var wrapped = _(array).push(3);

console.log(array);
// => [1, 2]

wrapped = wrapped.commit();
console.log(array);
// => [1, 2, 3]

wrapped.last();
// => 3

console.log(array);
// => [1, 2, 3]

static countBy

Creates an object composed of keys generated from the results of running
each element of collection thru iteratee. The corresponding value of
each key is the number of times the key was returned by iteratee. The
iteratee is invoked with one argument: (value).

Since:
  • 0.5.0
Example
_.countBy([6.1, 4.2, 6.3], Math.floor);
// => { '4': 1, '6': 2 }

// The `_.property` iteratee shorthand.
_.countBy(['one', 'two', 'three'], 'length');
// => { '3': 2, '5': 1 }

static defaults

Assigns own and inherited enumerable string keyed properties of source
objects to the destination object for all destination properties that
resolve to undefined. Source objects are applied from left to right.
Once a property is set, additional values of the same property are ignored.

Note: This method mutates object.

Since:
  • 0.1.0
See:
Example
_.defaults({ 'a': 1 }, { 'b': 2 }, { 'a': 3 });
// => { 'a': 1, 'b': 2 }

static defaultsDeep

This method is like _.defaults except that it recursively assigns
default properties.

Note: This method mutates object.

Since:
  • 3.10.0
See:
Example
_.defaultsDeep({ 'a': { 'b': 2 } }, { 'a': { 'b': 1, 'c': 3 } });
// => { 'a': { 'b': 2, 'c': 3 } }

static defer

Defers invoking the func until the current call stack has cleared. Any
additional arguments are provided to func when it's invoked.

Since:
  • 0.1.0
Example
_.defer(function(text) {
  console.log(text);
}, 'deferred');
// => Logs 'deferred' after one millisecond.

static delay

Invokes func after wait milliseconds. Any additional arguments are
provided to func when it's invoked.

Since:
  • 0.1.0
Example
_.delay(function(text) {
  console.log(text);
}, 1000, 'later');
// => Logs 'later' after one second.

static difference

Creates an array of array values not included in the other given arrays
using SameValueZero
for equality comparisons. The order and references of result values are
determined by the first array.

Note: Unlike _.pullAll, this method returns a new array.

Since:
  • 0.1.0
See:
  • _.without, _.xor
Example
_.difference([2, 1], [2, 3]);
// => [1]

static differenceBy

This method is like _.difference except that it accepts iteratee which
is invoked for each element of array and values to generate the criterion
by which they're compared. The order and references of result values are
determined by the first array. The iteratee is invoked with one argument:
(value).

Note: Unlike _.pullAllBy, this method returns a new array.

Since:
  • 4.0.0
Example
_.differenceBy([2.1, 1.2], [2.3, 3.4], Math.floor);
// => [1.2]

// The `_.property` iteratee shorthand.
_.differenceBy([{ 'x': 2 }, { 'x': 1 }], [{ 'x': 1 }], 'x');
// => [{ 'x': 2 }]

static differenceWith

This method is like _.difference except that it accepts comparator
which is invoked to compare elements of array to values. The order and
references of result values are determined by the first array. The comparator
is invoked with two arguments: (arrVal, othVal).

Note: Unlike _.pullAllWith, this method returns a new array.

Since:
  • 4.0.0
Example
var objects = [{ 'x': 1, 'y': 2 }, { 'x': 2, 'y': 1 }];

_.differenceWith(objects, [{ 'x': 1, 'y': 2 }], _.isEqual);
// => [{ 'x': 2, 'y': 1 }]

static divide

Divide two numbers.

Since:
  • 4.7.0
Example
_.divide(6, 4);
// => 1.5

static entries

Creates an array of own enumerable string keyed-value pairs for object
which can be consumed by _.fromPairs. If object is a map or set, its
entries are returned.

Since:
  • 4.0.0
Example
function Foo() {
  this.a = 1;
  this.b = 2;
}

Foo.prototype.c = 3;

_.toPairs(new Foo);
// => [['a', 1], ['b', 2]] (iteration order is not guaranteed)

static entriesIn

Creates an array of own and inherited enumerable string keyed-value pairs
for object which can be consumed by _.fromPairs. If object is a map
or set, its entries are returned.

Since:
  • 4.0.0
Example
function Foo() {
  this.a = 1;
  this.b = 2;
}

Foo.prototype.c = 3;

_.toPairsIn(new Foo);
// => [['a', 1], ['b', 2], ['c', 3]] (iteration order is not guaranteed)

static extend

This method is like _.assign except that it iterates over own and
inherited source properties.

Note: This method mutates object.

Since:
  • 4.0.0
See:
Example
function Foo() {
  this.a = 1;
}

function Bar() {
  this.c = 3;
}

Foo.prototype.b = 2;
Bar.prototype.d = 4;

_.assignIn({ 'a': 0 }, new Foo, new Bar);
// => { 'a': 1, 'b': 2, 'c': 3, 'd': 4 }

static extendWith

This method is like _.assignIn except that it accepts customizer
which is invoked to produce the assigned values. If customizer returns
undefined, assignment is handled by the method instead. The customizer
is invoked with five arguments: (objValue, srcValue, key, object, source).

Note: This method mutates object.

Since:
  • 4.0.0
See:
Example
function customizer(objValue, srcValue) {
  return _.isUndefined(objValue) ? srcValue : objValue;
}

var defaults = _.partialRight(_.assignInWith, customizer);

defaults({ 'a': 1 }, { 'b': 2 }, { 'a': 3 });
// => { 'a': 1, 'b': 2 }

static find

Iterates over elements of collection, returning the first element
predicate returns truthy for. The predicate is invoked with three
arguments: (value, index|key, collection).

Since:
  • 0.1.0
Example
var users = [
  { 'user': 'barney',  'age': 36, 'active': true },
  { 'user': 'fred',    'age': 40, 'active': false },
  { 'user': 'pebbles', 'age': 1,  'active': true }
];

_.find(users, function(o) { return o.age < 40; });
// => object for 'barney'

// The `_.matches` iteratee shorthand.
_.find(users, { 'age': 1, 'active': true });
// => object for 'pebbles'

// The `_.matchesProperty` iteratee shorthand.
_.find(users, ['active', false]);
// => object for 'fred'

// The `_.property` iteratee shorthand.
_.find(users, 'active');
// => object for 'barney'

static findLast

This method is like _.find except that it iterates over elements of
collection from right to left.

Since:
  • 2.0.0
Example
_.findLast([1, 2, 3, 4], function(n) {
  return n % 2 == 1;
});
// => 3

static floor

Computes number rounded down to precision.

Since:
  • 3.10.0
Example
_.floor(4.006);
// => 4

_.floor(0.046, 2);
// => 0.04

_.floor(4060, -2);
// => 4000

static flow

Creates a function that returns the result of invoking the given functions
with the this binding of the created function, where each successive
invocation is supplied the return value of the previous.

Since:
  • 3.0.0
See:
Example
function square(n) {
  return n * n;
}

var addSquare = _.flow([_.add, square]);
addSquare(1, 2);
// => 9

static flowRight

This method is like _.flow except that it creates a function that
invokes the given functions from right to left.

Since:
  • 3.0.0
See:
Example
function square(n) {
  return n * n;
}

var addSquare = _.flowRight([square, _.add]);
addSquare(1, 2);
// => 9

static groupBy

Creates an object composed of keys generated from the results of running
each element of collection thru iteratee. The order of grouped values
is determined by the order they occur in collection. The corresponding
value of each key is an array of elements responsible for generating the
key. The iteratee is invoked with one argument: (value).

Since:
  • 0.1.0
Example
_.groupBy([6.1, 4.2, 6.3], Math.floor);
// => { '4': [4.2], '6': [6.1, 6.3] }

// The `_.property` iteratee shorthand.
_.groupBy(['one', 'two', 'three'], 'length');
// => { '3': ['one', 'two'], '5': ['three'] }

static gt

Checks if value is greater than other.

Since:
  • 3.9.0
See:
Example
_.gt(3, 1);
// => true

_.gt(3, 3);
// => false

_.gt(1, 3);
// => false

static gte

Checks if value is greater than or equal to other.

Since:
  • 3.9.0
See:
Example
_.gte(3, 1);
// => true

_.gte(3, 3);
// => true

_.gte(1, 3);
// => false

static intersection

Creates an array of unique values that are included in all given arrays
using SameValueZero
for equality comparisons. The order and references of result values are
determined by the first array.

Since:
  • 0.1.0
Example
_.intersection([2, 1], [2, 3]);
// => [2]

static intersectionBy

This method is like _.intersection except that it accepts iteratee
which is invoked for each element of each arrays to generate the criterion
by which they're compared. The order and references of result values are
determined by the first array. The iteratee is invoked with one argument:
(value).

Since:
  • 4.0.0
Example
_.intersectionBy([2.1, 1.2], [2.3, 3.4], Math.floor);
// => [2.1]

// The `_.property` iteratee shorthand.
_.intersectionBy([{ 'x': 1 }], [{ 'x': 2 }, { 'x': 1 }], 'x');
// => [{ 'x': 1 }]

static intersectionWith

This method is like _.intersection except that it accepts comparator
which is invoked to compare elements of arrays. The order and references
of result values are determined by the first array. The comparator is
invoked with two arguments: (arrVal, othVal).

Since:
  • 4.0.0
Example
var objects = [{ 'x': 1, 'y': 2 }, { 'x': 2, 'y': 1 }];
var others = [{ 'x': 1, 'y': 1 }, { 'x': 1, 'y': 2 }];

_.intersectionWith(objects, others, _.isEqual);
// => [{ 'x': 1, 'y': 2 }]

static invert

Creates an object composed of the inverted keys and values of object.
If object contains duplicate values, subsequent values overwrite
property assignments of previous values.

Since:
  • 0.7.0
Example
var object = { 'a': 1, 'b': 2, 'c': 1 };

_.invert(object);
// => { '1': 'c', '2': 'b' }

static invertBy

This method is like _.invert except that the inverted object is generated
from the results of running each element of object thru iteratee. The
corresponding inverted value of each inverted key is an array of keys
responsible for generating the inverted value. The iteratee is invoked
with one argument: (value).

Since:
  • 4.1.0
Example
var object = { 'a': 1, 'b': 2, 'c': 1 };

_.invertBy(object);
// => { '1': ['a', 'c'], '2': ['b'] }

_.invertBy(object, function(value) {
  return 'group' + value;
});
// => { 'group1': ['a', 'c'], 'group2': ['b'] }

static invoke

Invokes the method at path of object.

Since:
  • 4.0.0
Example
var object = { 'a': [{ 'b': { 'c': [1, 2, 3, 4] } }] };

_.invoke(object, 'a[0].b.c.slice', 1, 3);
// => [2, 3]

static invokeMap

Invokes the method at path of each element in collection, returning
an array of the results of each invoked method. Any additional arguments
are provided to each invoked method. If path is a function, it's invoked
for, and this bound to, each element in collection.

Since:
  • 4.0.0
Example
_.invokeMap([[5, 1, 7], [3, 2, 1]], 'sort');
// => [[1, 5, 7], [1, 2, 3]]

_.invokeMap([123, 456], String.prototype.split, '');
// => [['1', '2', '3'], ['4', '5', '6']]

static isArguments

Checks if value is likely an arguments object.

Since:
  • 0.1.0
Example
_.isArguments(function() { return arguments; }());
// => true

_.isArguments([1, 2, 3]);
// => false

static isArray

Checks if value is classified as an Array object.

Since:
  • 0.1.0
Example
_.isArray([1, 2, 3]);
// => true

_.isArray(document.body.children);
// => false

_.isArray('abc');
// => false

_.isArray(_.noop);
// => false

static isArrayBuffer

Checks if value is classified as an ArrayBuffer object.

Since:
  • 4.3.0
Example
_.isArrayBuffer(new ArrayBuffer(2));
// => true

_.isArrayBuffer(new Array(2));
// => false

static isBuffer

Checks if value is a buffer.

Since:
  • 4.3.0
Example
_.isBuffer(new Buffer(2));
// => true

_.isBuffer(new Uint8Array(2));
// => false

static isDate

Checks if value is classified as a Date object.

Since:
  • 0.1.0
Example
_.isDate(new Date);
// => true

_.isDate('Mon April 23 2012');
// => false

static isMap

Checks if value is classified as a Map object.

Since:
  • 4.3.0
Example
_.isMap(new Map);
// => true

_.isMap(new WeakMap);
// => false

static isRegExp

Checks if value is classified as a RegExp object.

Since:
  • 0.1.0
Example
_.isRegExp(/abc/);
// => true

_.isRegExp('/abc/');
// => false

static isSet

Checks if value is classified as a Set object.

Since:
  • 4.3.0
Example
_.isSet(new Set);
// => true

_.isSet(new WeakSet);
// => false

static isTypedArray

Checks if value is classified as a typed array.

Since:
  • 3.0.0
Example
_.isTypedArray(new Uint8Array);
// => true

_.isTypedArray([]);
// => false

static kebabCase

Converts string to
kebab case.

Since:
  • 3.0.0
Example
_.kebabCase('Foo Bar');
// => 'foo-bar'

_.kebabCase('fooBar');
// => 'foo-bar'

_.kebabCase('__FOO_BAR__');
// => 'foo-bar'

static keyBy

Creates an object composed of keys generated from the results of running
each element of collection thru iteratee. The corresponding value of
each key is the last element responsible for generating the key. The
iteratee is invoked with one argument: (value).

Since:
  • 4.0.0
Example
var array = [
  { 'dir': 'left', 'code': 97 },
  { 'dir': 'right', 'code': 100 }
];

_.keyBy(array, function(o) {
  return String.fromCharCode(o.code);
});
// => { 'a': { 'dir': 'left', 'code': 97 }, 'd': { 'dir': 'right', 'code': 100 } }

_.keyBy(array, 'dir');
// => { 'left': { 'dir': 'left', 'code': 97 }, 'right': { 'dir': 'right', 'code': 100 } }

static lowerCase

Converts string, as space separated words, to lower case.

Since:
  • 4.0.0
Example
_.lowerCase('--Foo-Bar--');
// => 'foo bar'

_.lowerCase('fooBar');
// => 'foo bar'

_.lowerCase('__FOO_BAR__');
// => 'foo bar'

static lowerFirst

Converts the first character of string to lower case.

Since:
  • 4.0.0
Example
_.lowerFirst('Fred');
// => 'fred'

_.lowerFirst('FRED');
// => 'fRED'

static lt

Checks if value is less than other.

Since:
  • 3.9.0
See:
Example
_.lt(1, 3);
// => true

_.lt(3, 3);
// => false

_.lt(3, 1);
// => false

static lte

Checks if value is less than or equal to other.

Since:
  • 3.9.0
See:
Example
_.lte(1, 3);
// => true

_.lte(3, 3);
// => true

_.lte(3, 1);
// => false

static merge

This method is like _.assign except that it recursively merges own and
inherited enumerable string keyed properties of source objects into the
destination object. Source properties that resolve to undefined are
skipped if a destination value exists. Array and plain object properties
are merged recursively. Other objects and value types are overridden by
assignment. Source objects are applied from left to right. Subsequent
sources overwrite property assignments of previous sources.

Note: This method mutates object.

Since:
  • 0.5.0
Example
var object = {
  'a': [{ 'b': 2 }, { 'd': 4 }]
};

var other = {
  'a': [{ 'c': 3 }, { 'e': 5 }]
};

_.merge(object, other);
// => { 'a': [{ 'b': 2, 'c': 3 }, { 'd': 4, 'e': 5 }] }

static mergeWith

This method is like _.merge except that it accepts customizer which
is invoked to produce the merged values of the destination and source
properties. If customizer returns undefined, merging is handled by the
method instead. The customizer is invoked with six arguments:
(objValue, srcValue, key, object, source, stack).

Note: This method mutates object.

Since:
  • 4.0.0
Example
function customizer(objValue, srcValue) {
  if (_.isArray(objValue)) {
    return objValue.concat(srcValue);
  }
}

var object = { 'a': [1], 'b': [2] };
var other = { 'a': [3], 'b': [4] };

_.mergeWith(object, other, customizer);
// => { 'a': [1, 3], 'b': [2, 4] }

static method

Creates a function that invokes the method at path of a given object.
Any additional arguments are provided to the invoked method.

Since:
  • 3.7.0
Example
var objects = [
  { 'a': { 'b': _.constant(2) } },
  { 'a': { 'b': _.constant(1) } }
];

_.map(objects, _.method('a.b'));
// => [2, 1]

_.map(objects, _.method(['a', 'b']));
// => [2, 1]

static methodOf

The opposite of _.method; this method creates a function that invokes
the method at a given path of object. Any additional arguments are
provided to the invoked method.

Since:
  • 3.7.0
Example
var array = _.times(3, _.constant),
    object = { 'a': array, 'b': array, 'c': array };

_.map(['a[2]', 'c[0]'], _.methodOf(object));
// => [2, 0]

_.map([['a', '2'], ['c', '0']], _.methodOf(object));
// => [2, 0]

static multiply

Multiply two numbers.

Since:
  • 4.7.0
Example
_.multiply(6, 4);
// => 24

static next

Gets the next value on a wrapped object following the
iterator protocol.

Since:
  • 4.0.0
Example
var wrapped = _([1, 2]);

wrapped.next();
// => { 'done': false, 'value': 1 }

wrapped.next();
// => { 'done': false, 'value': 2 }

wrapped.next();
// => { 'done': true, 'value': undefined }

static now

Gets the timestamp of the number of milliseconds that have elapsed since
the Unix epoch (1 January 1970 00:00:00 UTC).

Since:
  • 2.4.0
Example
_.defer(function(stamp) {
  console.log(_.now() - stamp);
}, _.now());
// => Logs the number of milliseconds it took for the deferred invocation.

static omit

The opposite of _.pick; this method creates an object composed of the
own and inherited enumerable property paths of object that are not omitted.

Note: This method is considerably slower than _.pick.

Since:
  • 0.1.0
Example
var object = { 'a': 1, 'b': '2', 'c': 3 };

_.omit(object, ['a', 'c']);
// => { 'b': '2' }

static over

Creates a function that invokes iteratees with the arguments it receives
and returns their results.

Since:
  • 4.0.0
Example
var func = _.over([Math.max, Math.min]);

func(1, 2, 3, 4);
// => [4, 1]

static overArgs

Creates a function that invokes func with its arguments transformed.

Since:
  • 4.0.0
Example
function doubled(n) {
  return n * 2;
}

function square(n) {
  return n * n;
}

var func = _.overArgs(function(x, y) {
  return [x, y];
}, [square, doubled]);

func(9, 3);
// => [81, 6]

func(10, 5);
// => [100, 10]

static overEvery

Creates a function that checks if all of the predicates return
truthy when invoked with the arguments it receives.

Since:
  • 4.0.0
Example
var func = _.overEvery([Boolean, isFinite]);

func('1');
// => true

func(null);
// => false

func(NaN);
// => false

static overSome

Creates a function that checks if any of the predicates return
truthy when invoked with the arguments it receives.

Since:
  • 4.0.0
Example
var func = _.overSome([Boolean, isFinite]);

func('1');
// => true

func(null);
// => true

func(NaN);
// => false

static partial

Creates a function that invokes func with partials prepended to the
arguments it receives. This method is like _.bind except it does not
alter the this binding.

The _.partial.placeholder value, which defaults to _ in monolithic
builds, may be used as a placeholder for partially applied arguments.

Note: This method doesn't set the "length" property of partially
applied functions.

Since:
  • 0.2.0
Example
function greet(greeting, name) {
  return greeting + ' ' + name;
}

var sayHelloTo = _.partial(greet, 'hello');
sayHelloTo('fred');
// => 'hello fred'

// Partially applied with placeholders.
var greetFred = _.partial(greet, _, 'fred');
greetFred('hi');
// => 'hi fred'

static partialRight

This method is like _.partial except that partially applied arguments
are appended to the arguments it receives.

The _.partialRight.placeholder value, which defaults to _ in monolithic
builds, may be used as a placeholder for partially applied arguments.

Note: This method doesn't set the "length" property of partially
applied functions.

Since:
  • 1.0.0
Example
function greet(greeting, name) {
  return greeting + ' ' + name;
}

var greetFred = _.partialRight(greet, 'fred');
greetFred('hi');
// => 'hi fred'

// Partially applied with placeholders.
var sayHelloTo = _.partialRight(greet, 'hello', _);
sayHelloTo('fred');
// => 'hello fred'

static partition

Creates an array of elements split into two groups, the first of which
contains elements predicate returns truthy for, the second of which
contains elements predicate returns falsey for. The predicate is
invoked with one argument: (value).

Since:
  • 3.0.0
Example
var users = [
  { 'user': 'barney',  'age': 36, 'active': false },
  { 'user': 'fred',    'age': 40, 'active': true },
  { 'user': 'pebbles', 'age': 1,  'active': false }
];

_.partition(users, function(o) { return o.active; });
// => objects for [['fred'], ['barney', 'pebbles']]

// The `_.matches` iteratee shorthand.
_.partition(users, { 'age': 1, 'active': false });
// => objects for [['pebbles'], ['barney', 'fred']]

// The `_.matchesProperty` iteratee shorthand.
_.partition(users, ['active', false]);
// => objects for [['barney', 'pebbles'], ['fred']]

// The `_.property` iteratee shorthand.
_.partition(users, 'active');
// => objects for [['fred'], ['barney', 'pebbles']]

static pick

Creates an object composed of the picked object properties.

Since:
  • 0.1.0
Example
var object = { 'a': 1, 'b': '2', 'c': 3 };

_.pick(object, ['a', 'c']);
// => { 'a': 1, 'c': 3 }

static plant

Creates a clone of the chain sequence planting value as the wrapped value.

Since:
  • 3.2.0
Example
function square(n) {
  return n * n;
}

var wrapped = _([1, 2]).map(square);
var other = wrapped.plant([3, 4]);

other.value();
// => [9, 16]

wrapped.value();
// => [1, 4]

static pull

Removes all given values from array using
SameValueZero
for equality comparisons.

Note: Unlike _.without, this method mutates array. Use _.remove
to remove elements from an array by predicate.

Since:
  • 2.0.0
Example
var array = ['a', 'b', 'c', 'a', 'b', 'c'];

_.pull(array, 'a', 'c');
console.log(array);
// => ['b', 'b']

static pullAt

Removes elements from array corresponding to indexes and returns an
array of removed elements.

Note: Unlike _.at, this method mutates array.

Since:
  • 3.0.0
Example
var array = ['a', 'b', 'c', 'd'];
var pulled = _.pullAt(array, [1, 3]);

console.log(array);
// => ['a', 'c']

console.log(pulled);
// => ['b', 'd']

static range

Creates an array of numbers (positive and/or negative) progressing from
start up to, but not including, end. A step of -1 is used if a negative
start is specified without an end or step. If end is not specified,
it's set to start with start then set to 0.

Note: JavaScript follows the IEEE-754 standard for resolving
floating-point values which can produce unexpected results.

Since:
  • 0.1.0
See:
  • _.inRange, _.rangeRight
Example
_.range(4);
// => [0, 1, 2, 3]

_.range(-4);
// => [0, -1, -2, -3]

_.range(1, 5);
// => [1, 2, 3, 4]

_.range(0, 20, 5);
// => [0, 5, 10, 15]

_.range(0, -4, -1);
// => [0, -1, -2, -3]

_.range(1, 4, 0);
// => [1, 1, 1]

_.range(0);
// => []

static rangeRight

This method is like _.range except that it populates values in
descending order.

Since:
  • 4.0.0
See:
  • _.inRange, _.range
Example
_.rangeRight(4);
// => [3, 2, 1, 0]

_.rangeRight(-4);
// => [-3, -2, -1, 0]

_.rangeRight(1, 5);
// => [4, 3, 2, 1]

_.rangeRight(0, 20, 5);
// => [15, 10, 5, 0]

_.rangeRight(0, -4, -1);
// => [-3, -2, -1, 0]

_.rangeRight(1, 4, 0);
// => [1, 1, 1]

_.rangeRight(0);
// => []

static rearg

Creates a function that invokes func with arguments arranged according
to the specified indexes where the argument value at the first index is
provided as the first argument, the argument value at the second index is
provided as the second argument, and so on.

Since:
  • 3.0.0
Example
var rearged = _.rearg(function(a, b, c) {
  return [a, b, c];
}, [2, 0, 1]);

rearged('b', 'c', 'a')
// => ['a', 'b', 'c']

static reverse

This method is the wrapper version of _.reverse.

Note: This method mutates the wrapped array.

Since:
  • 0.1.0
Example
var array = [1, 2, 3];

_(array).reverse().value()
// => [3, 2, 1]

console.log(array);
// => [3, 2, 1]

static round

Computes number rounded to precision.

Since:
  • 3.10.0
Example
_.round(4.006);
// => 4

_.round(4.006, 2);
// => 4.01

_.round(4060, -2);
// => 4100

static snakeCase

Converts string to
snake case.

Since:
  • 3.0.0
Example
_.snakeCase('Foo Bar');
// => 'foo_bar'

_.snakeCase('fooBar');
// => 'foo_bar'

_.snakeCase('--FOO-BAR--');
// => 'foo_bar'

static sortBy

Creates an array of elements, sorted in ascending order by the results of
running each element in a collection thru each iteratee. This method
performs a stable sort, that is, it preserves the original sort order of
equal elements. The iteratees are invoked with one argument: (value).

Since:
  • 0.1.0
Example
var users = [
  { 'user': 'fred',   'age': 48 },
  { 'user': 'barney', 'age': 36 },
  { 'user': 'fred',   'age': 40 },
  { 'user': 'barney', 'age': 34 }
];

_.sortBy(users, [function(o) { return o.user; }]);
// => objects for [['barney', 36], ['barney', 34], ['fred', 48], ['fred', 40]]

_.sortBy(users, ['user', 'age']);
// => objects for [['barney', 34], ['barney', 36], ['fred', 40], ['fred', 48]]

static startCase

Converts string to
start case.

Since:
  • 3.1.0
Example
_.startCase('--foo-bar--');
// => 'Foo Bar'

_.startCase('fooBar');
// => 'Foo Bar'

_.startCase('__FOO_BAR__');
// => 'FOO BAR'

static subtract

Subtract two numbers.

Since:
  • 4.0.0
Example
_.subtract(6, 4);
// => 2

static union

Creates an array of unique values, in order, from all given arrays using
SameValueZero
for equality comparisons.

Since:
  • 0.1.0
Example
_.union([2], [1, 2]);
// => [2, 1]

static unionBy

This method is like _.union except that it accepts iteratee which is
invoked for each element of each arrays to generate the criterion by
which uniqueness is computed. Result values are chosen from the first
array in which the value occurs. The iteratee is invoked with one argument:
(value).

Since:
  • 4.0.0
Example
_.unionBy([2.1], [1.2, 2.3], Math.floor);
// => [2.1, 1.2]

// The `_.property` iteratee shorthand.
_.unionBy([{ 'x': 1 }], [{ 'x': 2 }, { 'x': 1 }], 'x');
// => [{ 'x': 1 }, { 'x': 2 }]

static unionWith

This method is like _.union except that it accepts comparator which
is invoked to compare elements of arrays. Result values are chosen from
the first array in which the value occurs. The comparator is invoked
with two arguments: (arrVal, othVal).

Since:
  • 4.0.0
Example
var objects = [{ 'x': 1, 'y': 2 }, { 'x': 2, 'y': 1 }];
var others = [{ 'x': 1, 'y': 1 }, { 'x': 1, 'y': 2 }];

_.unionWith(objects, others, _.isEqual);
// => [{ 'x': 1, 'y': 2 }, { 'x': 2, 'y': 1 }, { 'x': 1, 'y': 1 }]

static upperCase

Converts string, as space separated words, to upper case.

Since:
  • 4.0.0
Example
_.upperCase('--foo-bar');
// => 'FOO BAR'

_.upperCase('fooBar');
// => 'FOO BAR'

_.upperCase('__foo_bar__');
// => 'FOO BAR'

static upperFirst

Converts the first character of string to upper case.

Since:
  • 4.0.0
Example
_.upperFirst('fred');
// => 'Fred'

_.upperFirst('FRED');
// => 'FRED'

static without

Creates an array excluding all given values using
SameValueZero
for equality comparisons.

Note: Unlike _.pull, this method returns a new array.

Since:
  • 0.1.0
See:
  • _.difference, _.xor
Example
_.without([2, 1, 2, 3], 1, 2);
// => [3]

static xor

Creates an array of unique values that is the
symmetric difference
of the given arrays. The order of result values is determined by the order
they occur in the arrays.

Since:
  • 2.4.0
See:
  • _.difference, _.without
Example
_.xor([2, 1], [2, 3]);
// => [1, 3]

static xorBy

This method is like _.xor except that it accepts iteratee which is
invoked for each element of each arrays to generate the criterion by
which by which they're compared. The order of result values is determined
by the order they occur in the arrays. The iteratee is invoked with one
argument: (value).

Since:
  • 4.0.0
Example
_.xorBy([2.1, 1.2], [2.3, 3.4], Math.floor);
// => [1.2, 3.4]

// The `_.property` iteratee shorthand.
_.xorBy([{ 'x': 1 }], [{ 'x': 2 }, { 'x': 1 }], 'x');
// => [{ 'x': 2 }]

static xorWith

This method is like _.xor except that it accepts comparator which is
invoked to compare elements of arrays. The order of result values is
determined by the order they occur in the arrays. The comparator is invoked
with two arguments: (arrVal, othVal).

Since:
  • 4.0.0
Example
var objects = [{ 'x': 1, 'y': 2 }, { 'x': 2, 'y': 1 }];
var others = [{ 'x': 1, 'y': 1 }, { 'x': 1, 'y': 2 }];

_.xorWith(objects, others, _.isEqual);
// => [{ 'x': 2, 'y': 1 }, { 'x': 1, 'y': 1 }]

static zip

Creates an array of grouped elements, the first of which contains the
first elements of the given arrays, the second of which contains the
second elements of the given arrays, and so on.

Since:
  • 0.1.0
Example
_.zip(['a', 'b'], [1, 2], [true, false]);
// => [['a', 1, true], ['b', 2, false]]

static zipWith

This method is like _.zip except that it accepts iteratee to specify
how grouped values should be combined. The iteratee is invoked with the
elements of each group: (...group).

Since:
  • 3.8.0
Example
_.zipWith([1, 2], [10, 20], [100, 200], function(a, b, c) {
  return a + b + c;
});
// => [111, 222]

value

Executes the chain sequence to resolve the unwrapped value.

Since:
  • 0.1.0
Example
_([1, 2, 3]).value();
// => [1, 2, 3]

Methods

static after(n, func) → {function}

The opposite of _.before; this method creates a function that invokes
func once it's called n or more times.

Parameters:
Name Type Description
n number

The number of calls before func is invoked.

func function

The function to restrict.

Returns:
function -

Returns the new restricted function.

Since:
  • 0.1.0
Example
var saves = ['profile', 'settings'];

var done = _.after(saves.length, function() {
  console.log('done saving!');
});

_.forEach(saves, function(type) {
  asyncSave({ 'type': type, 'complete': done });
});
// => Logs 'done saving!' after the two async saves have completed.

static ary(func, nopt) → {function}

Creates a function that invokes func, with up to n arguments,
ignoring any additional arguments.

Parameters:
Name Type Attributes Default Description
func function

The function to cap arguments for.

n number <optional>
func.length

The arity cap.

Returns:
function -

Returns the new capped function.

Since:
  • 3.0.0
Example
_.map(['6', '8', '10'], _.ary(parseInt, 1));
// => [6, 8, 10]

static before(n, func) → {function}

Creates a function that invokes func, with the this binding and arguments
of the created function, while it's called less than n times. Subsequent
calls to the created function return the result of the last func invocation.

Parameters:
Name Type Description
n number

The number of calls at which func is no longer invoked.

func function

The function to restrict.

Returns:
function -

Returns the new restricted function.

Since:
  • 3.0.0
Example
jQuery(element).on('click', _.before(5, addContactToList));
// => Allows adding up to 4 contacts to the list.

static capitalize(stringopt) → {string}

Converts the first character of string to upper case and the remaining
to lower case.

Parameters:
Name Type Attributes Default Description
string string <optional>
''

The string to capitalize.

Returns:
string -

Returns the capitalized string.

Since:
  • 3.0.0
Example
_.capitalize('FRED');
// => 'Fred'

static castArray(value) → {Array}

Casts value as an array if it's not one.

Parameters:
Name Type Description
value *

The value to inspect.

Returns:
Array -

Returns the cast array.

Since:
  • 4.4.0
Example
_.castArray(1);
// => [1]

_.castArray({ 'a': 1 });
// => [{ 'a': 1 }]

_.castArray('abc');
// => ['abc']

_.castArray(null);
// => [null]

_.castArray(undefined);
// => [undefined]

_.castArray();
// => []

var array = [1, 2, 3];
console.log(_.castArray(array) === array);
// => true

static chain(value) → {Object}

Creates a lodash wrapper instance that wraps value with explicit method
chain sequences enabled. The result of such sequences must be unwrapped
with _#value.

Parameters:
Name Type Description
value *

The value to wrap.

Returns:
Object -

Returns the new lodash wrapper instance.

Since:
  • 1.3.0
Example
var users = [
  { 'user': 'barney',  'age': 36 },
  { 'user': 'fred',    'age': 40 },
  { 'user': 'pebbles', 'age': 1 }
];

var youngest = _
  .chain(users)
  .sortBy('age')
  .map(function(o) {
    return o.user + ' is ' + o.age;
  })
  .head()
  .value();
// => 'pebbles is 1'

static chunk(array, sizeopt) → {Array}

Creates an array of elements split into groups the length of size.
If array can't be split evenly, the final chunk will be the remaining
elements.

Parameters:
Name Type Attributes Default Description
array Array

The array to process.

size number <optional>
1

The length of each chunk

Returns:
Array -

Returns the new array of chunks.

Since:
  • 3.0.0
Example
_.chunk(['a', 'b', 'c', 'd'], 2);
// => [['a', 'b'], ['c', 'd']]

_.chunk(['a', 'b', 'c', 'd'], 3);
// => [['a', 'b', 'c'], ['d']]

static clamp(number, loweropt, upper) → {number}

Clamps number within the inclusive lower and upper bounds.

Parameters:
Name Type Attributes Description
number number

The number to clamp.

lower number <optional>

The lower bound.

upper number

The upper bound.

Returns:
number -

Returns the clamped number.

Since:
  • 4.0.0
Example
_.clamp(-10, -5, 5);
// => -5

_.clamp(10, -5, 5);
// => 5

static clone(value) → {*}

Creates a shallow clone of value.

Note: This method is loosely based on the
structured clone algorithm
and supports cloning arrays, array buffers, booleans, date objects, maps,
numbers, Object objects, regexes, sets, strings, symbols, and typed
arrays. The own enumerable properties of arguments objects are cloned
as plain objects. An empty object is returned for uncloneable values such
as error objects, functions, DOM nodes, and WeakMaps.

Parameters:
Name Type Description
value *

The value to clone.

Returns:
* -

Returns the cloned value.

Since:
  • 0.1.0
See:
Example
var objects = [{ 'a': 1 }, { 'b': 2 }];

var shallow = _.clone(objects);
console.log(shallow[0] === objects[0]);
// => true

static cloneDeep(value) → {*}

This method is like _.clone except that it recursively clones value.

Parameters:
Name Type Description
value *

The value to recursively clone.

Returns:
* -

Returns the deep cloned value.

Since:
  • 1.0.0
See:
Example
var objects = [{ 'a': 1 }, { 'b': 2 }];

var deep = _.cloneDeep(objects);
console.log(deep[0] === objects[0]);
// => false

static cloneDeepWith(value, customizeropt) → {*}

This method is like _.cloneWith except that it recursively clones value.

Parameters:
Name Type Attributes Description
value *

The value to recursively clone.

customizer function <optional>

The function to customize cloning.

Returns:
* -

Returns the deep cloned value.

Since:
  • 4.0.0
See:
Example
function customizer(value) {
  if (_.isElement(value)) {
    return value.cloneNode(true);
  }
}

var el = _.cloneDeepWith(document.body, customizer);

console.log(el === document.body);
// => false
console.log(el.nodeName);
// => 'BODY'
console.log(el.childNodes.length);
// => 20

static cloneWith(value, customizeropt) → {*}

This method is like _.clone except that it accepts customizer which
is invoked to produce the cloned value. If customizer returns undefined,
cloning is handled by the method instead. The customizer is invoked with
up to four arguments; (value [, index|key, object, stack]).

Parameters:
Name Type Attributes Description
value *

The value to clone.

customizer function <optional>

The function to customize cloning.

Returns:
* -

Returns the cloned value.

Since:
  • 4.0.0
See:
Example
function customizer(value) {
  if (_.isElement(value)) {
    return value.cloneNode(false);
  }
}

var el = _.cloneWith(document.body, customizer);

console.log(el === document.body);
// => false
console.log(el.nodeName);
// => 'BODY'
console.log(el.childNodes.length);
// => 0

static compact(array) → {Array}

Creates an array with all falsey values removed. The values false, null,
0, "", undefined, and NaN are falsey.

Parameters:
Name Type Description
array Array

The array to compact.

Returns:
Array -

Returns the new array of filtered values.

Since:
  • 0.1.0
Example
_.compact([0, 1, false, 2, '', 3]);
// => [1, 2, 3]

static concat(array, …valuesopt) → {Array}

Creates a new array concatenating array with any additional arrays
and/or values.

Parameters:
Name Type Attributes Description
array Array

The array to concatenate.

values * <optional>
<repeatable>

The values to concatenate.

Returns:
Array -

Returns the new concatenated array.

Since:
  • 4.0.0
Example
var array = [1];
var other = _.concat(array, 2, [3], [[4]]);

console.log(other);
// => [1, 2, 3, [4]]

console.log(array);
// => [1]

static cond(pairs) → {function}

Creates a function that iterates over pairs and invokes the corresponding
function of the first predicate to return truthy. The predicate-function
pairs are invoked with the this binding and arguments of the created
function.

Parameters:
Name Type Description
pairs Array

The predicate-function pairs.

Returns:
function -

Returns the new composite function.

Since:
  • 4.0.0
Example
var func = _.cond([
  [_.matches({ 'a': 1 }),           _.constant('matches A')],
  [_.conforms({ 'b': _.isNumber }), _.constant('matches B')],
  [_.stubTrue,                      _.constant('no match')]
]);

func({ 'a': 1, 'b': 2 });
// => 'matches A'

func({ 'a': 0, 'b': 1 });
// => 'matches B'

func({ 'a': '1', 'b': '2' });
// => 'no match'

static conforms(source) → {function}

Creates a function that invokes the predicate properties of source with
the corresponding property values of a given object, returning true if
all predicates return truthy, else false.

Note: The created function is equivalent to _.conformsTo with
source partially applied.

Parameters:
Name Type Description
source Object

The object of property predicates to conform to.

Returns:
function -

Returns the new spec function.

Since:
  • 4.0.0
Example
var objects = [
  { 'a': 2, 'b': 1 },
  { 'a': 1, 'b': 2 }
];

_.filter(objects, _.conforms({ 'b': function(n) { return n > 1; } }));
// => [{ 'a': 1, 'b': 2 }]

static conformsTo(object, source) → {boolean}

Checks if object conforms to source by invoking the predicate
properties of source with the corresponding property values of object.

Note: This method is equivalent to _.conforms when source is
partially applied.

Parameters:
Name Type Description
object Object

The object to inspect.

source Object

The object of property predicates to conform to.

Returns:
boolean -

Returns true if object conforms, else false.

Since:
  • 4.14.0
Example
var object = { 'a': 1, 'b': 2 };

_.conformsTo(object, { 'b': function(n) { return n > 1; } });
// => true

_.conformsTo(object, { 'b': function(n) { return n > 2; } });
// => false

static constant(value) → {function}

Creates a function that returns value.

Parameters:
Name Type Description
value *

The value to return from the new function.

Returns:
function -

Returns the new constant function.

Since:
  • 2.4.0
Example
var objects = _.times(2, _.constant({ 'a': 1 }));

console.log(objects);
// => [{ 'a': 1 }, { 'a': 1 }]

console.log(objects[0] === objects[1]);
// => true

static create(prototype, propertiesopt) → {Object}

Creates an object that inherits from the prototype object. If a
properties object is given, its own enumerable string keyed properties
are assigned to the created object.

Parameters:
Name Type Attributes Description
prototype Object

The object to inherit from.

properties Object <optional>

The properties to assign to the object.

Returns:
Object -

Returns the new object.

Since:
  • 2.3.0
Example
function Shape() {
  this.x = 0;
  this.y = 0;
}

function Circle() {
  Shape.call(this);
}

Circle.prototype = _.create(Shape.prototype, {
  'constructor': Circle
});

var circle = new Circle;
circle instanceof Circle;
// => true

circle instanceof Shape;
// => true

static curry(func, arityopt) → {function}

Creates a function that accepts arguments of func and either invokes
func returning its result, if at least arity number of arguments have
been provided, or returns a function that accepts the remaining func
arguments, and so on. The arity of func may be specified if func.length
is not sufficient.

The _.curry.placeholder value, which defaults to _ in monolithic builds,
may be used as a placeholder for provided arguments.

Note: This method doesn't set the "length" property of curried functions.

Parameters:
Name Type Attributes Default Description
func function

The function to curry.

arity number <optional>
func.length

The arity of func.

Returns:
function -

Returns the new curried function.

Since:
  • 2.0.0
Example
var abc = function(a, b, c) {
  return [a, b, c];
};

var curried = _.curry(abc);

curried(1)(2)(3);
// => [1, 2, 3]

curried(1, 2)(3);
// => [1, 2, 3]

curried(1, 2, 3);
// => [1, 2, 3]

// Curried with placeholders.
curried(1)(_, 3)(2);
// => [1, 2, 3]

static curryRight(func, arityopt) → {function}

This method is like _.curry except that arguments are applied to func
in the manner of _.partialRight instead of _.partial.

The _.curryRight.placeholder value, which defaults to _ in monolithic
builds, may be used as a placeholder for provided arguments.

Note: This method doesn't set the "length" property of curried functions.

Parameters:
Name Type Attributes Default Description
func function

The function to curry.

arity number <optional>
func.length

The arity of func.

Returns:
function -

Returns the new curried function.

Since:
  • 3.0.0
Example
var abc = function(a, b, c) {
  return [a, b, c];
};

var curried = _.curryRight(abc);

curried(3)(2)(1);
// => [1, 2, 3]

curried(2, 3)(1);
// => [1, 2, 3]

curried(1, 2, 3);
// => [1, 2, 3]

// Curried with placeholders.
curried(3)(1, _)(2);
// => [1, 2, 3]

static debounce(func, waitopt, optionsopt) → {function}

Creates a debounced function that delays invoking func until after wait
milliseconds have elapsed since the last time the debounced function was
invoked. The debounced function comes with a cancel method to cancel
delayed func invocations and a flush method to immediately invoke them.
Provide options to indicate whether func should be invoked on the
leading and/or trailing edge of the wait timeout. The func is invoked
with the last arguments provided to the debounced function. Subsequent
calls to the debounced function return the result of the last func
invocation.

Note: If leading and trailing options are true, func is
invoked on the trailing edge of the timeout only if the debounced function
is invoked more than once during the wait timeout.

If wait is 0 and leading is false, func invocation is deferred
until to the next tick, similar to setTimeout with a timeout of 0.

See David Corbacho's article
for details over the differences between _.debounce and _.throttle.

Parameters:
Name Type Attributes Default Description
func function

The function to debounce.

wait number <optional>
0

The number of milliseconds to delay.

options Object <optional>
{}

The options object.

Properties
Name Type Attributes Default Description
leading boolean <optional>
false

Specify invoking on the leading edge of the timeout.

maxWait number <optional>

The maximum time func is allowed to be delayed before it's invoked.

trailing boolean <optional>
true

Specify invoking on the trailing edge of the timeout.

Returns:
function -

Returns the new debounced function.

Since:
  • 0.1.0
Example
// Avoid costly calculations while the window size is in flux.
jQuery(window).on('resize', _.debounce(calculateLayout, 150));

// Invoke `sendMail` when clicked, debouncing subsequent calls.
jQuery(element).on('click', _.debounce(sendMail, 300, {
  'leading': true,
  'trailing': false
}));

// Ensure `batchLog` is invoked once after 1 second of debounced calls.
var debounced = _.debounce(batchLog, 250, { 'maxWait': 1000 });
var source = new EventSource('/stream');
jQuery(source).on('message', debounced);

// Cancel the trailing debounced invocation.
jQuery(window).on('popstate', debounced.cancel);

static deburr(stringopt) → {string}

Deburrs string by converting
Latin-1 Supplement
and Latin Extended-A
letters to basic Latin letters and removing
combining diacritical marks.

Parameters:
Name Type Attributes Default Description
string string <optional>
''

The string to deburr.

Returns:
string -

Returns the deburred string.

Since:
  • 3.0.0
Example
_.deburr('déjà vu');
// => 'deja vu'

static defaultTo(value, defaultValue) → {*}

Checks value to determine whether a default value should be returned in
its place. The defaultValue is returned if value is NaN, null,
or undefined.

Parameters:
Name Type Description
value *

The value to check.

defaultValue *

The default value.

Returns:
* -

Returns the resolved value.

Since:
  • 4.14.0
Example
_.defaultTo(1, 10);
// => 1

_.defaultTo(undefined, 10);
// => 10

static drop(array, nopt) → {Array}

Creates a slice of array with n elements dropped from the beginning.

Parameters:
Name Type Attributes Default Description
array Array

The array to query.

n number <optional>
1

The number of elements to drop.

Returns:
Array -

Returns the slice of array.

Since:
  • 0.5.0
Example
_.drop([1, 2, 3]);
// => [2, 3]

_.drop([1, 2, 3], 2);
// => [3]

_.drop([1, 2, 3], 5);
// => []

_.drop([1, 2, 3], 0);
// => [1, 2, 3]

static dropRight(array, nopt) → {Array}

Creates a slice of array with n elements dropped from the end.

Parameters:
Name Type Attributes Default Description
array Array

The array to query.

n number <optional>
1

The number of elements to drop.

Returns:
Array -

Returns the slice of array.

Since:
  • 3.0.0
Example
_.dropRight([1, 2, 3]);
// => [1, 2]

_.dropRight([1, 2, 3], 2);
// => [1]

_.dropRight([1, 2, 3], 5);
// => []

_.dropRight([1, 2, 3], 0);
// => [1, 2, 3]

static dropRightWhile(array, predicateopt) → {Array}

Creates a slice of array excluding elements dropped from the end.
Elements are dropped until predicate returns falsey. The predicate is
invoked with three arguments: (value, index, array).

Parameters:
Name Type Attributes Default Description
array Array

The array to query.

predicate function <optional>
_.identity

The function invoked per iteration.

Returns:
Array -

Returns the slice of array.

Since:
  • 3.0.0
Example
var users = [
  { 'user': 'barney',  'active': true },
  { 'user': 'fred',    'active': false },
  { 'user': 'pebbles', 'active': false }
];

_.dropRightWhile(users, function(o) { return !o.active; });
// => objects for ['barney']

// The `_.matches` iteratee shorthand.
_.dropRightWhile(users, { 'user': 'pebbles', 'active': false });
// => objects for ['barney', 'fred']

// The `_.matchesProperty` iteratee shorthand.
_.dropRightWhile(users, ['active', false]);
// => objects for ['barney']

// The `_.property` iteratee shorthand.
_.dropRightWhile(users, 'active');
// => objects for ['barney', 'fred', 'pebbles']

static dropWhile(array, predicateopt) → {Array}

Creates a slice of array excluding elements dropped from the beginning.
Elements are dropped until predicate returns falsey. The predicate is
invoked with three arguments: (value, index, array).

Parameters:
Name Type Attributes Default Description
array Array

The array to query.

predicate function <optional>
_.identity

The function invoked per iteration.

Returns:
Array -

Returns the slice of array.

Since:
  • 3.0.0
Example
var users = [
  { 'user': 'barney',  'active': false },
  { 'user': 'fred',    'active': false },
  { 'user': 'pebbles', 'active': true }
];

_.dropWhile(users, function(o) { return !o.active; });
// => objects for ['pebbles']

// The `_.matches` iteratee shorthand.
_.dropWhile(users, { 'user': 'barney', 'active': false });
// => objects for ['fred', 'pebbles']

// The `_.matchesProperty` iteratee shorthand.
_.dropWhile(users, ['active', false]);
// => objects for ['pebbles']

// The `_.property` iteratee shorthand.
_.dropWhile(users, 'active');
// => objects for ['barney', 'fred', 'pebbles']

static each(collection, iterateeopt) → {Array|Object}

Iterates over elements of collection and invokes iteratee for each element.
The iteratee is invoked with three arguments: (value, index|key, collection).
Iteratee functions may exit iteration early by explicitly returning false.

Note: As with other "Collections" methods, objects with a "length"
property are iterated like arrays. To avoid this behavior use _.forIn
or _.forOwn for object iteration.

Parameters:
Name Type Attributes Default Description
collection Array | Object

The collection to iterate over.

iteratee function <optional>
_.identity

The function invoked per iteration.

Returns:
Array | Object -

Returns collection.

Since:
  • 0.1.0
See:
  • _.forEachRight
Example
_.forEach([1, 2], function(value) {
  console.log(value);
});
// => Logs `1` then `2`.

_.forEach({ 'a': 1, 'b': 2 }, function(value, key) {
  console.log(key);
});
// => Logs 'a' then 'b' (iteration order is not guaranteed).

static eachRight(collection, iterateeopt) → {Array|Object}

This method is like _.forEach except that it iterates over elements of
collection from right to left.

Parameters:
Name Type Attributes Default Description
collection Array | Object

The collection to iterate over.

iteratee function <optional>
_.identity

The function invoked per iteration.

Returns:
Array | Object -

Returns collection.

Since:
  • 2.0.0
See:
  • _.forEach
Example
_.forEachRight([1, 2], function(value) {
  console.log(value);
});
// => Logs `2` then `1`.

static endsWith(stringopt, targetopt, positionopt) → {boolean}

Checks if string ends with the given target string.

Parameters:
Name Type Attributes Default Description
string string <optional>
''

The string to inspect.

target string <optional>

The string to search for.

position number <optional>
string.length

The position to search up to.

Returns:
boolean -

Returns true if string ends with target,
else false.

Since:
  • 3.0.0
Example
_.endsWith('abc', 'c');
// => true

_.endsWith('abc', 'b');
// => false

_.endsWith('abc', 'b', 2);
// => true

static eq(value, other) → {boolean}

Performs a
SameValueZero
comparison between two values to determine if they are equivalent.

Parameters:
Name Type Description
value *

The value to compare.

other *

The other value to compare.

Returns:
boolean -

Returns true if the values are equivalent, else false.

Since:
  • 4.0.0
Example
var object = { 'a': 1 };
var other = { 'a': 1 };

_.eq(object, object);
// => true

_.eq(object, other);
// => false

_.eq('a', 'a');
// => true

_.eq('a', Object('a'));
// => false

_.eq(NaN, NaN);
// => true

static escape(stringopt) → {string}

Converts the characters "&", "<", ">", '"', and "'" in string to their
corresponding HTML entities.

Note: No other characters are escaped. To escape additional
characters use a third-party library like he.

Though the ">" character is escaped for symmetry, characters like
">" and "/" don't need escaping in HTML and have no special meaning
unless they're part of a tag or unquoted attribute value. See
Mathias Bynens's article
(under "semi-related fun fact") for more details.

When working with HTML you should always
quote attribute values to reduce
XSS vectors.

Parameters:
Name Type Attributes Default Description
string string <optional>
''

The string to escape.

Returns:
string -

Returns the escaped string.

Since:
  • 0.1.0
Example
_.escape('fred, barney, & pebbles');
// => 'fred, barney, &amp; pebbles'

static escapeRegExp(stringopt) → {string}

Escapes the RegExp special characters "^", "$", "", ".", "*", "+",
"?", "(", ")", "[", "]", "{", "}", and "|" in string.

Parameters:
Name Type Attributes Default Description
string string <optional>
''

The string to escape.

Returns:
string -

Returns the escaped string.

Since:
  • 3.0.0
Example
_.escapeRegExp('[lodash](https://lodash.com/)');
// => '\[lodash\]\(https://lodash\.com/\)'

static every(collection, predicateopt) → {boolean}

Checks if predicate returns truthy for all elements of collection.
Iteration is stopped once predicate returns falsey. The predicate is
invoked with three arguments: (value, index|key, collection).

Note: This method returns true for
empty collections because
everything is true of
elements of empty collections.

Parameters:
Name Type Attributes Default Description
collection Array | Object

The collection to iterate over.

predicate function <optional>
_.identity

The function invoked per iteration.

Returns:
boolean -

Returns true if all elements pass the predicate check,
else false.

Since:
  • 0.1.0
Example
_.every([true, 1, null, 'yes'], Boolean);
// => false

var users = [
  { 'user': 'barney', 'age': 36, 'active': false },
  { 'user': 'fred',   'age': 40, 'active': false }
];

// The `_.matches` iteratee shorthand.
_.every(users, { 'user': 'barney', 'active': false });
// => false

// The `_.matchesProperty` iteratee shorthand.
_.every(users, ['active', false]);
// => true

// The `_.property` iteratee shorthand.
_.every(users, 'active');
// => false

static fill(array, value, startopt, endopt) → {Array}

Fills elements of array with value from start up to, but not
including, end.

Note: This method mutates array.

Parameters:
Name Type Attributes Default Description
array Array

The array to fill.

value *

The value to fill array with.

start number <optional>
0

The start position.

end number <optional>
array.length

The end position.

Returns:
Array -

Returns array.

Since:
  • 3.2.0
Example
var array = [1, 2, 3];

_.fill(array, 'a');
console.log(array);
// => ['a', 'a', 'a']

_.fill(Array(3), 2);
// => [2, 2, 2]

_.fill([4, 6, 8, 10], '*', 1, 3);
// => [4, '*', '*', 10]

static filter(collection, predicateopt) → {Array}

Iterates over elements of collection, returning an array of all elements
predicate returns truthy for. The predicate is invoked with three
arguments: (value, index|key, collection).

Note: Unlike _.remove, this method returns a new array.

Parameters:
Name Type Attributes Default Description
collection Array | Object

The collection to iterate over.

predicate function <optional>
_.identity

The function invoked per iteration.

Returns:
Array -

Returns the new filtered array.

Since:
  • 0.1.0
See:
Example
var users = [
  { 'user': 'barney', 'age': 36, 'active': true },
  { 'user': 'fred',   'age': 40, 'active': false }
];

_.filter(users, function(o) { return !o.active; });
// => objects for ['fred']

// The `_.matches` iteratee shorthand.
_.filter(users, { 'age': 36, 'active': true });
// => objects for ['barney']

// The `_.matchesProperty` iteratee shorthand.
_.filter(users, ['active', false]);
// => objects for ['fred']

// The `_.property` iteratee shorthand.
_.filter(users, 'active');
// => objects for ['barney']

static findIndex(array, predicateopt, fromIndexopt) → {number}

This method is like _.find except that it returns the index of the first
element predicate returns truthy for instead of the element itself.

Parameters:
Name Type Attributes Default Description
array Array

The array to inspect.

predicate function <optional>
_.identity

The function invoked per iteration.

fromIndex number <optional>
0

The index to search from.

Returns:
number -

Returns the index of the found element, else -1.

Since:
  • 1.1.0
Example
var users = [
  { 'user': 'barney',  'active': false },
  { 'user': 'fred',    'active': false },
  { 'user': 'pebbles', 'active': true }
];

_.findIndex(users, function(o) { return o.user == 'barney'; });
// => 0

// The `_.matches` iteratee shorthand.
_.findIndex(users, { 'user': 'fred', 'active': false });
// => 1

// The `_.matchesProperty` iteratee shorthand.
_.findIndex(users, ['active', false]);
// => 0

// The `_.property` iteratee shorthand.
_.findIndex(users, 'active');
// => 2

static findKey(object, predicateopt) → {string|undefined}

This method is like _.find except that it returns the key of the first
element predicate returns truthy for instead of the element itself.

Parameters:
Name Type Attributes Default Description
object Object

The object to inspect.

predicate function <optional>
_.identity

The function invoked per iteration.

Returns:
string | undefined -

Returns the key of the matched element,
else undefined.

Since:
  • 1.1.0
Example
var users = {
  'barney':  { 'age': 36, 'active': true },
  'fred':    { 'age': 40, 'active': false },
  'pebbles': { 'age': 1,  'active': true }
};

_.findKey(users, function(o) { return o.age < 40; });
// => 'barney' (iteration order is not guaranteed)

// The `_.matches` iteratee shorthand.
_.findKey(users, { 'age': 1, 'active': true });
// => 'pebbles'

// The `_.matchesProperty` iteratee shorthand.
_.findKey(users, ['active', false]);
// => 'fred'

// The `_.property` iteratee shorthand.
_.findKey(users, 'active');
// => 'barney'

static findLastIndex(array, predicateopt, fromIndexopt) → {number}

This method is like _.findIndex except that it iterates over elements
of collection from right to left.

Parameters:
Name Type Attributes Default Description
array Array

The array to inspect.

predicate function <optional>
_.identity

The function invoked per iteration.

fromIndex number <optional>
array.length-1

The index to search from.

Returns:
number -

Returns the index of the found element, else -1.

Since:
  • 2.0.0
Example
var users = [
  { 'user': 'barney',  'active': true },
  { 'user': 'fred',    'active': false },
  { 'user': 'pebbles', 'active': false }
];

_.findLastIndex(users, function(o) { return o.user == 'pebbles'; });
// => 2

// The `_.matches` iteratee shorthand.
_.findLastIndex(users, { 'user': 'barney', 'active': true });
// => 0

// The `_.matchesProperty` iteratee shorthand.
_.findLastIndex(users, ['active', false]);
// => 2

// The `_.property` iteratee shorthand.
_.findLastIndex(users, 'active');
// => 0

static findLastKey(object, predicateopt) → {string|undefined}

This method is like _.findKey except that it iterates over elements of
a collection in the opposite order.

Parameters:
Name Type Attributes Default Description
object Object

The object to inspect.

predicate function <optional>
_.identity

The function invoked per iteration.

Returns:
string | undefined -

Returns the key of the matched element,
else undefined.

Since:
  • 2.0.0
Example
var users = {
  'barney':  { 'age': 36, 'active': true },
  'fred':    { 'age': 40, 'active': false },
  'pebbles': { 'age': 1,  'active': true }
};

_.findLastKey(users, function(o) { return o.age < 40; });
// => returns 'pebbles' assuming `_.findKey` returns 'barney'

// The `_.matches` iteratee shorthand.
_.findLastKey(users, { 'age': 36, 'active': true });
// => 'barney'

// The `_.matchesProperty` iteratee shorthand.
_.findLastKey(users, ['active', false]);
// => 'fred'

// The `_.property` iteratee shorthand.
_.findLastKey(users, 'active');
// => 'pebbles'

static first(array) → {*}

Gets the first element of array.

Parameters:
Name Type Description
array Array

The array to query.

Returns:
* -

Returns the first element of array.

Since:
  • 0.1.0
Example
_.head([1, 2, 3]);
// => 1

_.head([]);
// => undefined

static flatMap(collection, iterateeopt) → {Array}

Creates a flattened array of values by running each element in collection
thru iteratee and flattening the mapped results. The iteratee is invoked
with three arguments: (value, index|key, collection).

Parameters:
Name Type Attributes Default Description
collection Array | Object

The collection to iterate over.

iteratee function <optional>
_.identity

The function invoked per iteration.

Returns:
Array -

Returns the new flattened array.

Since:
  • 4.0.0
Example
function duplicate(n) {
  return [n, n];
}

_.flatMap([1, 2], duplicate);
// => [1, 1, 2, 2]

static flatMapDeep(collection, iterateeopt) → {Array}

This method is like _.flatMap except that it recursively flattens the
mapped results.

Parameters:
Name Type Attributes Default Description
collection Array | Object

The collection to iterate over.

iteratee function <optional>
_.identity

The function invoked per iteration.

Returns:
Array -

Returns the new flattened array.

Since:
  • 4.7.0
Example
function duplicate(n) {
  return [[[n, n]]];
}

_.flatMapDeep([1, 2], duplicate);
// => [1, 1, 2, 2]

static flatMapDepth(collection, iterateeopt, depthopt) → {Array}

This method is like _.flatMap except that it recursively flattens the
mapped results up to depth times.

Parameters:
Name Type Attributes Default Description
collection Array | Object

The collection to iterate over.

iteratee function <optional>
_.identity

The function invoked per iteration.

depth number <optional>
1

The maximum recursion depth.

Returns:
Array -

Returns the new flattened array.

Since:
  • 4.7.0
Example
function duplicate(n) {
  return [[[n, n]]];
}

_.flatMapDepth([1, 2], duplicate, 2);
// => [[1, 1], [2, 2]]

static flatten(array) → {Array}

Flattens array a single level deep.

Parameters:
Name Type Description
array Array

The array to flatten.

Returns:
Array -

Returns the new flattened array.

Since:
  • 0.1.0
Example
_.flatten([1, [2, [3, [4]], 5]]);
// => [1, 2, [3, [4]], 5]

static flattenDeep(array) → {Array}

Recursively flattens array.

Parameters:
Name Type Description
array Array

The array to flatten.

Returns:
Array -

Returns the new flattened array.

Since:
  • 3.0.0
Example
_.flattenDeep([1, [2, [3, [4]], 5]]);
// => [1, 2, 3, 4, 5]

static flattenDepth(array, depthopt) → {Array}

Recursively flatten array up to depth times.

Parameters:
Name Type Attributes Default Description
array Array

The array to flatten.

depth number <optional>
1

The maximum recursion depth.

Returns:
Array -

Returns the new flattened array.

Since:
  • 4.4.0
Example
var array = [1, [2, [3, [4]], 5]];

_.flattenDepth(array, 1);
// => [1, 2, [3, [4]], 5]

_.flattenDepth(array, 2);
// => [1, 2, 3, [4], 5]

static flip(func) → {function}

Creates a function that invokes func with arguments reversed.

Parameters:
Name Type Description
func function

The function to flip arguments for.

Returns:
function -

Returns the new flipped function.

Since:
  • 4.0.0
Example
var flipped = _.flip(function() {
  return _.toArray(arguments);
});

flipped('a', 'b', 'c', 'd');
// => ['d', 'c', 'b', 'a']

static forIn(object, iterateeopt) → {Object}

Iterates over own and inherited enumerable string keyed properties of an
object and invokes iteratee for each property. The iteratee is invoked
with three arguments: (value, key, object). Iteratee functions may exit
iteration early by explicitly returning false.

Parameters:
Name Type Attributes Default Description
object Object

The object to iterate over.

iteratee function <optional>
_.identity

The function invoked per iteration.

Returns:
Object -

Returns object.

Since:
  • 0.3.0
See:
Example
function Foo() {
  this.a = 1;
  this.b = 2;
}

Foo.prototype.c = 3;

_.forIn(new Foo, function(value, key) {
  console.log(key);
});
// => Logs 'a', 'b', then 'c' (iteration order is not guaranteed).

static forInRight(object, iterateeopt) → {Object}

This method is like _.forIn except that it iterates over properties of
object in the opposite order.

Parameters:
Name Type Attributes Default Description
object Object

The object to iterate over.

iteratee function <optional>
_.identity

The function invoked per iteration.

Returns:
Object -

Returns object.

Since:
  • 2.0.0
See:
Example
function Foo() {
  this.a = 1;
  this.b = 2;
}

Foo.prototype.c = 3;

_.forInRight(new Foo, function(value, key) {
  console.log(key);
});
// => Logs 'c', 'b', then 'a' assuming `_.forIn` logs 'a', 'b', then 'c'.

static forOwn(object, iterateeopt) → {Object}

Iterates over own enumerable string keyed properties of an object and
invokes iteratee for each property. The iteratee is invoked with three
arguments: (value, key, object). Iteratee functions may exit iteration
early by explicitly returning false.

Parameters:
Name Type Attributes Default Description
object Object

The object to iterate over.

iteratee function <optional>
_.identity

The function invoked per iteration.

Returns:
Object -

Returns object.

Since:
  • 0.3.0
See:
Example
function Foo() {
  this.a = 1;
  this.b = 2;
}

Foo.prototype.c = 3;

_.forOwn(new Foo, function(value, key) {
  console.log(key);
});
// => Logs 'a' then 'b' (iteration order is not guaranteed).

static forOwnRight(object, iterateeopt) → {Object}

This method is like _.forOwn except that it iterates over properties of
object in the opposite order.

Parameters:
Name Type Attributes Default Description
object Object

The object to iterate over.

iteratee function <optional>
_.identity

The function invoked per iteration.

Returns:
Object -

Returns object.

Since:
  • 2.0.0
See:
Example
function Foo() {
  this.a = 1;
  this.b = 2;
}

Foo.prototype.c = 3;

_.forOwnRight(new Foo, function(value, key) {
  console.log(key);
});
// => Logs 'b' then 'a' assuming `_.forOwn` logs 'a' then 'b'.

static fromPairs(pairs) → {Object}

The inverse of _.toPairs; this method returns an object composed
from key-value pairs.

Parameters:
Name Type Description
pairs Array

The key-value pairs.

Returns:
Object -

Returns the new object.

Since:
  • 4.0.0
Example
_.fromPairs([['a', 1], ['b', 2]]);
// => { 'a': 1, 'b': 2 }

static functions(object) → {Array}

Creates an array of function property names from own enumerable properties
of object.

Parameters:
Name Type Description
object Object

The object to inspect.

Returns:
Array -

Returns the function names.

Since:
  • 0.1.0
See:
Example
function Foo() {
  this.a = _.constant('a');
  this.b = _.constant('b');
}

Foo.prototype.c = _.constant('c');

_.functions(new Foo);
// => ['a', 'b']

static functionsIn(object) → {Array}

Creates an array of function property names from own and inherited
enumerable properties of object.

Parameters:
Name Type Description
object Object

The object to inspect.

Returns:
Array -

Returns the function names.

Since:
  • 4.0.0
See:
Example
function Foo() {
  this.a = _.constant('a');
  this.b = _.constant('b');
}

Foo.prototype.c = _.constant('c');

_.functionsIn(new Foo);
// => ['a', 'b', 'c']

static get(object, path, defaultValueopt) → {*}

Gets the value at path of object. If the resolved value is
undefined, the defaultValue is returned in its place.

Parameters:
Name Type Attributes Description
object Object

The object to query.

path Array | string

The path of the property to get.

defaultValue * <optional>

The value returned for undefined resolved values.

Returns:
* -

Returns the resolved value.

Since:
  • 3.7.0
Example
var object = { 'a': [{ 'b': { 'c': 3 } }] };

_.get(object, 'a[0].b.c');
// => 3

_.get(object, ['a', '0', 'b', 'c']);
// => 3

_.get(object, 'a.b.c', 'default');
// => 'default'

static has(object, path) → {boolean}

Checks if path is a direct property of object.

Parameters:
Name Type Description
object Object

The object to query.

path Array | string

The path to check.

Returns:
boolean -

Returns true if path exists, else false.

Since:
  • 0.1.0
Example
var object = { 'a': { 'b': 2 } };
var other = _.create({ 'a': _.create({ 'b': 2 }) });

_.has(object, 'a');
// => true

_.has(object, 'a.b');
// => true

_.has(object, ['a', 'b']);
// => true

_.has(other, 'a');
// => false

static hasIn(object, path) → {boolean}

Checks if path is a direct or inherited property of object.

Parameters:
Name Type Description
object Object

The object to query.

path Array | string

The path to check.

Returns:
boolean -

Returns true if path exists, else false.

Since:
  • 4.0.0
Example
var object = _.create({ 'a': _.create({ 'b': 2 }) });

_.hasIn(object, 'a');
// => true

_.hasIn(object, 'a.b');
// => true

_.hasIn(object, ['a', 'b']);
// => true

_.hasIn(object, 'b');
// => false

static identity(value) → {*}

This method returns the first argument it receives.

Parameters:
Name Type Description
value *

Any value.

Returns:
* -

Returns value.

Since:
  • 0.1.0
Example
var object = { 'a': 1 };

console.log(_.identity(object) === object);
// => true

static inRange(number, startopt, end) → {boolean}

Checks if n is between start and up to, but not including, end. If
end is not specified, it's set to start with start then set to 0.
If start is greater than end the params are swapped to support
negative ranges.

Parameters:
Name Type Attributes Default Description
number number

The number to check.

start number <optional>
0

The start of the range.

end number

The end of the range.

Returns:
boolean -

Returns true if number is in the range, else false.

Since:
  • 3.3.0
See:
  • _.range, _.rangeRight
Example
_.inRange(3, 2, 4);
// => true

_.inRange(4, 8);
// => true

_.inRange(4, 2);
// => false

_.inRange(2, 2);
// => false

_.inRange(1.2, 2);
// => true

_.inRange(5.2, 4);
// => false

_.inRange(-3, -2, -6);
// => true

static includes(collection, value, fromIndexopt) → {boolean}

Checks if value is in collection. If collection is a string, it's
checked for a substring of value, otherwise
SameValueZero
is used for equality comparisons. If fromIndex is negative, it's used as
the offset from the end of collection.

Parameters:
Name Type Attributes Default Description
collection Array | Object | string

The collection to inspect.

value *

The value to search for.

fromIndex number <optional>
0

The index to search from.

Returns:
boolean -

Returns true if value is found, else false.

Since:
  • 0.1.0
Example
_.includes([1, 2, 3], 1);
// => true

_.includes([1, 2, 3], 1, 2);
// => false

_.includes({ 'a': 1, 'b': 2 }, 1);
// => true

_.includes('abcd', 'bc');
// => true

static indexOf(array, value, fromIndexopt) → {number}

Gets the index at which the first occurrence of value is found in array
using SameValueZero
for equality comparisons. If fromIndex is negative, it's used as the
offset from the end of array.

Parameters:
Name Type Attributes Default Description
array Array

The array to inspect.

value *

The value to search for.

fromIndex number <optional>
0

The index to search from.

Returns:
number -

Returns the index of the matched value, else -1.

Since:
  • 0.1.0
Example
_.indexOf([1, 2, 1, 2], 2);
// => 1

// Search from the `fromIndex`.
_.indexOf([1, 2, 1, 2], 2, 2);
// => 3

static initial(array) → {Array}

Gets all but the last element of array.

Parameters:
Name Type Description
array Array

The array to query.

Returns:
Array -

Returns the slice of array.

Since:
  • 0.1.0
Example
_.initial([1, 2, 3]);
// => [1, 2]

static isArrayLike(value) → {boolean}

Checks if value is array-like. A value is considered array-like if it's
not a function and has a value.length that's an integer greater than or
equal to 0 and less than or equal to Number.MAX_SAFE_INTEGER.

Parameters:
Name Type Description
value *

The value to check.

Returns:
boolean -

Returns true if value is array-like, else false.

Since:
  • 4.0.0
Example
_.isArrayLike([1, 2, 3]);
// => true

_.isArrayLike(document.body.children);
// => true

_.isArrayLike('abc');
// => true

_.isArrayLike(_.noop);
// => false

static isArrayLikeObject(value) → {boolean}

This method is like _.isArrayLike except that it also checks if value
is an object.

Parameters:
Name Type Description
value *

The value to check.

Returns:
boolean -

Returns true if value is an array-like object,
else false.

Since:
  • 4.0.0
Example
_.isArrayLikeObject([1, 2, 3]);
// => true

_.isArrayLikeObject(document.body.children);
// => true

_.isArrayLikeObject('abc');
// => false

_.isArrayLikeObject(_.noop);
// => false

static isBoolean(value) → {boolean}

Checks if value is classified as a boolean primitive or object.

Parameters:
Name Type Description
value *

The value to check.

Returns:
boolean -

Returns true if value is a boolean, else false.

Since:
  • 0.1.0
Example
_.isBoolean(false);
// => true

_.isBoolean(null);
// => false

static isElement(value) → {boolean}

Checks if value is likely a DOM element.

Parameters:
Name Type Description
value *

The value to check.

Returns:
boolean -

Returns true if value is a DOM element, else false.

Since:
  • 0.1.0
Example
_.isElement(document.body);
// => true

_.isElement('<body>');
// => false

static isEmpty(value) → {boolean}

Checks if value is an empty object, collection, map, or set.

Objects are considered empty if they have no own enumerable string keyed
properties.

Array-like values such as arguments objects, arrays, buffers, strings, or
jQuery-like collections are considered empty if they have a length of 0.
Similarly, maps and sets are considered empty if they have a size of 0.

Parameters:
Name Type Description
value *

The value to check.

Returns:
boolean -

Returns true if value is empty, else false.

Since:
  • 0.1.0
Example
_.isEmpty(null);
// => true

_.isEmpty(true);
// => true

_.isEmpty(1);
// => true

_.isEmpty([1, 2, 3]);
// => false

_.isEmpty({ 'a': 1 });
// => false

static isEqual(value, other) → {boolean}

Performs a deep comparison between two values to determine if they are
equivalent.

Note: This method supports comparing arrays, array buffers, booleans,
date objects, error objects, maps, numbers, Object objects, regexes,
sets, strings, symbols, and typed arrays. Object objects are compared
by their own, not inherited, enumerable properties. Functions and DOM
nodes are compared by strict equality, i.e. ===.

Parameters:
Name Type Description
value *

The value to compare.

other *

The other value to compare.

Returns:
boolean -

Returns true if the values are equivalent, else false.

Since:
  • 0.1.0
Example
var object = { 'a': 1 };
var other = { 'a': 1 };

_.isEqual(object, other);
// => true

object === other;
// => false

static isEqualWith(value, other, customizeropt) → {boolean}

This method is like _.isEqual except that it accepts customizer which
is invoked to compare values. If customizer returns undefined, comparisons
are handled by the method instead. The customizer is invoked with up to
six arguments: (objValue, othValue [, index|key, object, other, stack]).

Parameters:
Name Type Attributes Description
value *

The value to compare.

other *

The other value to compare.

customizer function <optional>

The function to customize comparisons.

Returns:
boolean -

Returns true if the values are equivalent, else false.

Since:
  • 4.0.0
Example
function isGreeting(value) {
  return /^h(?:i|ello)$/.test(value);
}

function customizer(objValue, othValue) {
  if (isGreeting(objValue) && isGreeting(othValue)) {
    return true;
  }
}

var array = ['hello', 'goodbye'];
var other = ['hi', 'goodbye'];

_.isEqualWith(array, other, customizer);
// => true

static isError(value) → {boolean}

Checks if value is an Error, EvalError, RangeError, ReferenceError,
SyntaxError, TypeError, or URIError object.

Parameters:
Name Type Description
value *

The value to check.

Returns:
boolean -

Returns true if value is an error object, else false.

Since:
  • 3.0.0
Example
_.isError(new Error);
// => true

_.isError(Error);
// => false

static isFinite(value) → {boolean}

Checks if value is a finite primitive number.

Note: This method is based on
Number.isFinite.

Parameters:
Name Type Description
value *

The value to check.

Returns:
boolean -

Returns true if value is a finite number, else false.

Since:
  • 0.1.0
Example
_.isFinite(3);
// => true

_.isFinite(Number.MIN_VALUE);
// => true

_.isFinite(Infinity);
// => false

_.isFinite('3');
// => false

static isFunction(value) → {boolean}

Checks if value is classified as a Function object.

Parameters:
Name Type Description
value *

The value to check.

Returns:
boolean -

Returns true if value is a function, else false.

Since:
  • 0.1.0
Example
_.isFunction(_);
// => true

_.isFunction(/abc/);
// => false

static isInteger(value) → {boolean}

Checks if value is an integer.

Note: This method is based on
Number.isInteger.

Parameters:
Name Type Description
value *

The value to check.

Returns:
boolean -

Returns true if value is an integer, else false.

Since:
  • 4.0.0
Example
_.isInteger(3);
// => true

_.isInteger(Number.MIN_VALUE);
// => false

_.isInteger(Infinity);
// => false

_.isInteger('3');
// => false

static isLength(value) → {boolean}

Checks if value is a valid array-like length.

Note: This method is loosely based on
ToLength.

Parameters:
Name Type Description
value *

The value to check.

Returns:
boolean -

Returns true if value is a valid length, else false.

Since:
  • 4.0.0
Example
_.isLength(3);
// => true

_.isLength(Number.MIN_VALUE);
// => false

_.isLength(Infinity);
// => false

_.isLength('3');
// => false

static isMatch(object, source) → {boolean}

Performs a partial deep comparison between object and source to
determine if object contains equivalent property values.

Note: This method is equivalent to _.matches when source is
partially applied.

Partial comparisons will match empty array and empty object source
values against any array or object value, respectively. See _.isEqual
for a list of supported value comparisons.

Parameters:
Name Type Description
object Object

The object to inspect.

source Object

The object of property values to match.

Returns:
boolean -

Returns true if object is a match, else false.

Since:
  • 3.0.0
Example
var object = { 'a': 1, 'b': 2 };

_.isMatch(object, { 'b': 2 });
// => true

_.isMatch(object, { 'b': 1 });
// => false

static isMatchWith(object, source, customizeropt) → {boolean}

This method is like _.isMatch except that it accepts customizer which
is invoked to compare values. If customizer returns undefined, comparisons
are handled by the method instead. The customizer is invoked with five
arguments: (objValue, srcValue, index|key, object, source).

Parameters:
Name Type Attributes Description
object Object

The object to inspect.

source Object

The object of property values to match.

customizer function <optional>

The function to customize comparisons.

Returns:
boolean -

Returns true if object is a match, else false.

Since:
  • 4.0.0
Example
function isGreeting(value) {
  return /^h(?:i|ello)$/.test(value);
}

function customizer(objValue, srcValue) {
  if (isGreeting(objValue) && isGreeting(srcValue)) {
    return true;
  }
}

var object = { 'greeting': 'hello' };
var source = { 'greeting': 'hi' };

_.isMatchWith(object, source, customizer);
// => true

static isNaN(value) → {boolean}

Checks if value is NaN.

Note: This method is based on
Number.isNaN and is not the same as
global isNaN which returns true for
undefined and other non-number values.

Parameters:
Name Type Description
value *

The value to check.

Returns:
boolean -

Returns true if value is NaN, else false.

Since:
  • 0.1.0
Example
_.isNaN(NaN);
// => true

_.isNaN(new Number(NaN));
// => true

isNaN(undefined);
// => true

_.isNaN(undefined);
// => false

static isNative(value) → {boolean}

Checks if value is a pristine native function.

Note: This method can't reliably detect native functions in the presence
of the core-js package because core-js circumvents this kind of detection.
Despite multiple requests, the core-js maintainer has made it clear: any
attempt to fix the detection will be obstructed. As a result, we're left
with little choice but to throw an error. Unfortunately, this also affects
packages, like babel-polyfill,
which rely on core-js.

Parameters:
Name Type Description
value *

The value to check.

Returns:
boolean -

Returns true if value is a native function,
else false.

Since:
  • 3.0.0
Example
_.isNative(Array.prototype.push);
// => true

_.isNative(_);
// => false

static isNil(value) → {boolean}

Checks if value is null or undefined.

Parameters:
Name Type Description
value *

The value to check.

Returns:
boolean -

Returns true if value is nullish, else false.

Since:
  • 4.0.0
Example
_.isNil(null);
// => true

_.isNil(void 0);
// => true

_.isNil(NaN);
// => false

static isNull(value) → {boolean}

Checks if value is null.

Parameters:
Name Type Description
value *

The value to check.

Returns:
boolean -

Returns true if value is null, else false.

Since:
  • 0.1.0
Example
_.isNull(null);
// => true

_.isNull(void 0);
// => false

static isNumber(value) → {boolean}

Checks if value is classified as a Number primitive or object.

Note: To exclude Infinity, -Infinity, and NaN, which are
classified as numbers, use the _.isFinite method.

Parameters:
Name Type Description
value *

The value to check.

Returns:
boolean -

Returns true if value is a number, else false.

Since:
  • 0.1.0
Example
_.isNumber(3);
// => true

_.isNumber(Number.MIN_VALUE);
// => true

_.isNumber(Infinity);
// => true

_.isNumber('3');
// => false

static isObject(value) → {boolean}

Checks if value is the
language type
of Object. (e.g. arrays, functions, objects, regexes, new Number(0), and new String(''))

Parameters:
Name Type Description
value *

The value to check.

Returns:
boolean -

Returns true if value is an object, else false.

Since:
  • 0.1.0
Example
_.isObject({});
// => true

_.isObject([1, 2, 3]);
// => true

_.isObject(_.noop);
// => true

_.isObject(null);
// => false

static isObjectLike(value) → {boolean}

Checks if value is object-like. A value is object-like if it's not null
and has a typeof result of "object".

Parameters:
Name Type Description
value *

The value to check.

Returns:
boolean -

Returns true if value is object-like, else false.

Since:
  • 4.0.0
Example
_.isObjectLike({});
// => true

_.isObjectLike([1, 2, 3]);
// => true

_.isObjectLike(_.noop);
// => false

_.isObjectLike(null);
// => false

static isPlainObject(value) → {boolean}

Checks if value is a plain object, that is, an object created by the
Object constructor or one with a [[Prototype]] of null.

Parameters:
Name Type Description
value *

The value to check.

Returns:
boolean -

Returns true if value is a plain object, else false.

Since:
  • 0.8.0
Example
function Foo() {
  this.a = 1;
}

_.isPlainObject(new Foo);
// => false

_.isPlainObject([1, 2, 3]);
// => false

_.isPlainObject({ 'x': 0, 'y': 0 });
// => true

_.isPlainObject(Object.create(null));
// => true

static isSafeInteger(value) → {boolean}

Checks if value is a safe integer. An integer is safe if it's an IEEE-754
double precision number which isn't the result of a rounded unsafe integer.

Note: This method is based on
Number.isSafeInteger.

Parameters:
Name Type Description
value *

The value to check.

Returns:
boolean -

Returns true if value is a safe integer, else false.

Since:
  • 4.0.0
Example
_.isSafeInteger(3);
// => true

_.isSafeInteger(Number.MIN_VALUE);
// => false

_.isSafeInteger(Infinity);
// => false

_.isSafeInteger('3');
// => false

static isString(value) → {boolean}

Checks if value is classified as a String primitive or object.

Parameters:
Name Type Description
value *

The value to check.

Returns:
boolean -

Returns true if value is a string, else false.

Since:
  • 0.1.0
Example
_.isString('abc');
// => true

_.isString(1);
// => false

static isSymbol(value) → {boolean}

Checks if value is classified as a Symbol primitive or object.

Parameters:
Name Type Description
value *

The value to check.

Returns:
boolean -

Returns true if value is a symbol, else false.

Since:
  • 4.0.0
Example
_.isSymbol(Symbol.iterator);
// => true

_.isSymbol('abc');
// => false

static isUndefined(value) → {boolean}

Checks if value is undefined.

Parameters:
Name Type Description
value *

The value to check.

Returns:
boolean -

Returns true if value is undefined, else false.

Since:
  • 0.1.0
Example
_.isUndefined(void 0);
// => true

_.isUndefined(null);
// => false

static isWeakMap(value) → {boolean}

Checks if value is classified as a WeakMap object.

Parameters:
Name Type Description
value *

The value to check.

Returns:
boolean -

Returns true if value is a weak map, else false.

Since:
  • 4.3.0
Example
_.isWeakMap(new WeakMap);
// => true

_.isWeakMap(new Map);
// => false

static isWeakSet(value) → {boolean}

Checks if value is classified as a WeakSet object.

Parameters:
Name Type Description
value *

The value to check.

Returns:
boolean -

Returns true if value is a weak set, else false.

Since:
  • 4.3.0
Example
_.isWeakSet(new WeakSet);
// => true

_.isWeakSet(new Set);
// => false

static iteratee(funcopt) → {function}

Creates a function that invokes func with the arguments of the created
function. If func is a property name, the created function returns the
property value for a given element. If func is an array or object, the
created function returns true for elements that contain the equivalent
source properties, otherwise it returns false.

Parameters:
Name Type Attributes Default Description
func * <optional>
_.identity

The value to convert to a callback.

Returns:
function -

Returns the callback.

Since:
  • 4.0.0
Example
var users = [
  { 'user': 'barney', 'age': 36, 'active': true },
  { 'user': 'fred',   'age': 40, 'active': false }
];

// The `_.matches` iteratee shorthand.
_.filter(users, _.iteratee({ 'user': 'barney', 'active': true }));
// => [{ 'user': 'barney', 'age': 36, 'active': true }]

// The `_.matchesProperty` iteratee shorthand.
_.filter(users, _.iteratee(['user', 'fred']));
// => [{ 'user': 'fred', 'age': 40 }]

// The `_.property` iteratee shorthand.
_.map(users, _.iteratee('user'));
// => ['barney', 'fred']

// Create custom iteratee shorthands.
_.iteratee = _.wrap(_.iteratee, function(iteratee, func) {
  return !_.isRegExp(func) ? iteratee(func) : function(string) {
    return func.test(string);
  };
});

_.filter(['abc', 'def'], /ef/);
// => ['def']

static join(array, separatoropt) → {string}

Converts all elements in array into a string separated by separator.

Parameters:
Name Type Attributes Default Description
array Array

The array to convert.

separator string <optional>
','

The element separator.

Returns:
string -

Returns the joined string.

Since:
  • 4.0.0
Example
_.join(['a', 'b', 'c'], '~');
// => 'a~b~c'

static keys(object) → {Array}

Creates an array of the own enumerable property names of object.

Note: Non-object values are coerced to objects. See the
ES spec
for more details.

Parameters:
Name Type Description
object Object

The object to query.

Returns:
Array -

Returns the array of property names.

Since:
  • 0.1.0
Example
function Foo() {
  this.a = 1;
  this.b = 2;
}

Foo.prototype.c = 3;

_.keys(new Foo);
// => ['a', 'b'] (iteration order is not guaranteed)

_.keys('hi');
// => ['0', '1']

static keysIn(object) → {Array}

Creates an array of the own and inherited enumerable property names of object.

Note: Non-object values are coerced to objects.

Parameters:
Name Type Description
object Object

The object to query.

Returns:
Array -

Returns the array of property names.

Since:
  • 3.0.0
Example
function Foo() {
  this.a = 1;
  this.b = 2;
}

Foo.prototype.c = 3;

_.keysIn(new Foo);
// => ['a', 'b', 'c'] (iteration order is not guaranteed)

static last(array) → {*}

Gets the last element of array.

Parameters:
Name Type Description
array Array

The array to query.

Returns:
* -

Returns the last element of array.

Since:
  • 0.1.0
Example
_.last([1, 2, 3]);
// => 3

static lastIndexOf(array, value, fromIndexopt) → {number}

This method is like _.indexOf except that it iterates over elements of
array from right to left.

Parameters:
Name Type Attributes Default Description
array Array

The array to inspect.

value *

The value to search for.

fromIndex number <optional>
array.length-1

The index to search from.

Returns:
number -

Returns the index of the matched value, else -1.

Since:
  • 0.1.0
Example
_.lastIndexOf([1, 2, 1, 2], 2);
// => 3

// Search from the `fromIndex`.
_.lastIndexOf([1, 2, 1, 2], 2, 2);
// => 1

static map(collection, iterateeopt) → {Array}

Creates an array of values by running each element in collection thru
iteratee. The iteratee is invoked with three arguments:
(value, index|key, collection).

Many lodash methods are guarded to work as iteratees for methods like
_.every, _.filter, _.map, _.mapValues, _.reject, and _.some.

The guarded methods are:
ary, chunk, curry, curryRight, drop, dropRight, every,
fill, invert, parseInt, random, range, rangeRight, repeat,
sampleSize, slice, some, sortBy, split, take, takeRight,
template, trim, trimEnd, trimStart, and words

Parameters:
Name Type Attributes Default Description
collection Array | Object

The collection to iterate over.

iteratee function <optional>
_.identity

The function invoked per iteration.

Returns:
Array -

Returns the new mapped array.

Since:
  • 0.1.0
Example
function square(n) {
  return n * n;
}

_.map([4, 8], square);
// => [16, 64]

_.map({ 'a': 4, 'b': 8 }, square);
// => [16, 64] (iteration order is not guaranteed)

var users = [
  { 'user': 'barney' },
  { 'user': 'fred' }
];

// The `_.property` iteratee shorthand.
_.map(users, 'user');
// => ['barney', 'fred']

static mapKeys(object, iterateeopt) → {Object}

The opposite of _.mapValues; this method creates an object with the
same values as object and keys generated by running each own enumerable
string keyed property of object thru iteratee. The iteratee is invoked
with three arguments: (value, key, object).

Parameters:
Name Type Attributes Default Description
object Object

The object to iterate over.

iteratee function <optional>
_.identity

The function invoked per iteration.

Returns:
Object -

Returns the new mapped object.

Since:
  • 3.8.0
See:
Example
_.mapKeys({ 'a': 1, 'b': 2 }, function(value, key) {
  return key + value;
});
// => { 'a1': 1, 'b2': 2 }

static mapValues(object, iterateeopt) → {Object}

Creates an object with the same keys as object and values generated
by running each own enumerable string keyed property of object thru
iteratee. The iteratee is invoked with three arguments:
(value, key, object).

Parameters:
Name Type Attributes Default Description
object Object

The object to iterate over.

iteratee function <optional>
_.identity

The function invoked per iteration.

Returns:
Object -

Returns the new mapped object.

Since:
  • 2.4.0
See:
Example
var users = {
  'fred':    { 'user': 'fred',    'age': 40 },
  'pebbles': { 'user': 'pebbles', 'age': 1 }
};

_.mapValues(users, function(o) { return o.age; });
// => { 'fred': 40, 'pebbles': 1 } (iteration order is not guaranteed)

// The `_.property` iteratee shorthand.
_.mapValues(users, 'age');
// => { 'fred': 40, 'pebbles': 1 } (iteration order is not guaranteed)

static matches(source) → {function}

Creates a function that performs a partial deep comparison between a given
object and source, returning true if the given object has equivalent
property values, else false.

Note: The created function is equivalent to _.isMatch with source
partially applied.

Partial comparisons will match empty array and empty object source
values against any array or object value, respectively. See _.isEqual
for a list of supported value comparisons.

Parameters:
Name Type Description
source Object

The object of property values to match.

Returns:
function -

Returns the new spec function.

Since:
  • 3.0.0
Example
var objects = [
  { 'a': 1, 'b': 2, 'c': 3 },
  { 'a': 4, 'b': 5, 'c': 6 }
];

_.filter(objects, _.matches({ 'a': 4, 'c': 6 }));
// => [{ 'a': 4, 'b': 5, 'c': 6 }]

static matchesProperty(path, srcValue) → {function}

Creates a function that performs a partial deep comparison between the
value at path of a given object to srcValue, returning true if the
object value is equivalent, else false.

Note: Partial comparisons will match empty array and empty object
srcValue values against any array or object value, respectively. See
_.isEqual for a list of supported value comparisons.

Parameters:
Name Type Description
path Array | string

The path of the property to get.

srcValue *

The value to match.

Returns:
function -

Returns the new spec function.

Since:
  • 3.2.0
Example
var objects = [
  { 'a': 1, 'b': 2, 'c': 3 },
  { 'a': 4, 'b': 5, 'c': 6 }
];

_.find(objects, _.matchesProperty('a', 4));
// => { 'a': 4, 'b': 5, 'c': 6 }

static max(array) → {*}

Computes the maximum value of array. If array is empty or falsey,
undefined is returned.

Parameters:
Name Type Description
array Array

The array to iterate over.

Returns:
* -

Returns the maximum value.

Since:
  • 0.1.0
Example
_.max([4, 2, 8, 6]);
// => 8

_.max([]);
// => undefined

static maxBy(array, iterateeopt) → {*}

This method is like _.max except that it accepts iteratee which is
invoked for each element in array to generate the criterion by which
the value is ranked. The iteratee is invoked with one argument: (value).

Parameters:
Name Type Attributes Default Description
array Array

The array to iterate over.

iteratee function <optional>
_.identity

The iteratee invoked per element.

Returns:
* -

Returns the maximum value.

Since:
  • 4.0.0
Example
var objects = [{ 'n': 1 }, { 'n': 2 }];

_.maxBy(objects, function(o) { return o.n; });
// => { 'n': 2 }

// The `_.property` iteratee shorthand.
_.maxBy(objects, 'n');
// => { 'n': 2 }

static mean(array) → {number}

Computes the mean of the values in array.

Parameters:
Name Type Description
array Array

The array to iterate over.

Returns:
number -

Returns the mean.

Since:
  • 4.0.0
Example
_.mean([4, 2, 8, 6]);
// => 5

static meanBy(array, iterateeopt) → {number}

This method is like _.mean except that it accepts iteratee which is
invoked for each element in array to generate the value to be averaged.
The iteratee is invoked with one argument: (value).

Parameters:
Name Type Attributes Default Description
array Array

The array to iterate over.

iteratee function <optional>
_.identity

The iteratee invoked per element.

Returns:
number -

Returns the mean.

Since:
  • 4.7.0
Example
var objects = [{ 'n': 4 }, { 'n': 2 }, { 'n': 8 }, { 'n': 6 }];

_.meanBy(objects, function(o) { return o.n; });
// => 5

// The `_.property` iteratee shorthand.
_.meanBy(objects, 'n');
// => 5

static memoize(func, resolveropt) → {function}

Creates a function that memoizes the result of func. If resolver is
provided, it determines the cache key for storing the result based on the
arguments provided to the memoized function. By default, the first argument
provided to the memoized function is used as the map cache key. The func
is invoked with the this binding of the memoized function.

Note: The cache is exposed as the cache property on the memoized
function. Its creation may be customized by replacing the _.memoize.Cache
constructor with one whose instances implement the
Map
method interface of clear, delete, get, has, and set.

Parameters:
Name Type Attributes Description
func function

The function to have its output memoized.

resolver function <optional>

The function to resolve the cache key.

Returns:
function -

Returns the new memoized function.

Since:
  • 0.1.0
Example
var object = { 'a': 1, 'b': 2 };
var other = { 'c': 3, 'd': 4 };

var values = _.memoize(_.values);
values(object);
// => [1, 2]

values(other);
// => [3, 4]

object.a = 2;
values(object);
// => [1, 2]

// Modify the result cache.
values.cache.set(object, ['a', 'b']);
values(object);
// => ['a', 'b']

// Replace `_.memoize.Cache`.
_.memoize.Cache = WeakMap;

static min(array) → {*}

Computes the minimum value of array. If array is empty or falsey,
undefined is returned.

Parameters:
Name Type Description
array Array

The array to iterate over.

Returns:
* -

Returns the minimum value.

Since:
  • 0.1.0
Example
_.min([4, 2, 8, 6]);
// => 2

_.min([]);
// => undefined

static minBy(array, iterateeopt) → {*}

This method is like _.min except that it accepts iteratee which is
invoked for each element in array to generate the criterion by which
the value is ranked. The iteratee is invoked with one argument: (value).

Parameters:
Name Type Attributes Default Description
array Array

The array to iterate over.

iteratee function <optional>
_.identity

The iteratee invoked per element.

Returns:
* -

Returns the minimum value.

Since:
  • 4.0.0
Example
var objects = [{ 'n': 1 }, { 'n': 2 }];

_.minBy(objects, function(o) { return o.n; });
// => { 'n': 1 }

// The `_.property` iteratee shorthand.
_.minBy(objects, 'n');
// => { 'n': 1 }

static mixin(objectopt, source, optionsopt) → {function|Object}

Adds all own enumerable string keyed function properties of a source
object to the destination object. If object is a function, then methods
are added to its prototype as well.

Note: Use _.runInContext to create a pristine lodash function to
avoid conflicts caused by modifying the original.

Parameters:
Name Type Attributes Default Description
object function | Object <optional>
lodash

The destination object.

source Object

The object of functions to add.

options Object <optional>
{}

The options object.

Properties
Name Type Attributes Default Description
chain boolean <optional>
true

Specify whether mixins are chainable.

Returns:
function | Object -

Returns object.

Since:
  • 0.1.0
Example
function vowels(string) {
  return _.filter(string, function(v) {
    return /[aeiou]/i.test(v);
  });
}

_.mixin({ 'vowels': vowels });
_.vowels('fred');
// => ['e']

_('fred').vowels().value();
// => ['e']

_.mixin({ 'vowels': vowels }, { 'chain': false });
_('fred').vowels();
// => ['e']

static negate(predicate) → {function}

Creates a function that negates the result of the predicate func. The
func predicate is invoked with the this binding and arguments of the
created function.

Parameters:
Name Type Description
predicate function

The predicate to negate.

Returns:
function -

Returns the new negated function.

Since:
  • 3.0.0
Example
function isEven(n) {
  return n % 2 == 0;
}

_.filter([1, 2, 3, 4, 5, 6], _.negate(isEven));
// => [1, 3, 5]

static noConflict() → {function}

Reverts the _ variable to its previous value and returns a reference to
the lodash function.

Returns:
function -

Returns the lodash function.

Since:
  • 0.1.0
Example
var lodash = _.noConflict();

static noop()

This method returns undefined.

Since:
  • 2.3.0
Example
_.times(2, _.noop);
// => [undefined, undefined]

static nth(array, nopt) → {*}

Gets the element at index n of array. If n is negative, the nth
element from the end is returned.

Parameters:
Name Type Attributes Default Description
array Array

The array to query.

n number <optional>
0

The index of the element to return.

Returns:
* -

Returns the nth element of array.

Since:
  • 4.11.0
Example
var array = ['a', 'b', 'c', 'd'];

_.nth(array, 1);
// => 'b'

_.nth(array, -2);
// => 'c';

static nthArg(nopt) → {function}

Creates a function that gets the argument at index n. If n is negative,
the nth argument from the end is returned.

Parameters:
Name Type Attributes Default Description
n number <optional>
0

The index of the argument to return.

Returns:
function -

Returns the new pass-thru function.

Since:
  • 4.0.0
Example
var func = _.nthArg(1);
func('a', 'b', 'c', 'd');
// => 'b'

var func = _.nthArg(-2);
func('a', 'b', 'c', 'd');
// => 'c'

static omitBy(object, predicateopt) → {Object}

The opposite of _.pickBy; this method creates an object composed of
the own and inherited enumerable string keyed properties of object that
predicate doesn't return truthy for. The predicate is invoked with two
arguments: (value, key).

Parameters:
Name Type Attributes Default Description
object Object

The source object.

predicate function <optional>
_.identity

The function invoked per property.

Returns:
Object -

Returns the new object.

Since:
  • 4.0.0
Example
var object = { 'a': 1, 'b': '2', 'c': 3 };

_.omitBy(object, _.isNumber);
// => { 'b': '2' }

static once(func) → {function}

Creates a function that is restricted to invoking func once. Repeat calls
to the function return the value of the first invocation. The func is
invoked with the this binding and arguments of the created function.

Parameters:
Name Type Description
func function

The function to restrict.

Returns:
function -

Returns the new restricted function.

Since:
  • 0.1.0
Example
var initialize = _.once(createApplication);
initialize();
initialize();
// => `createApplication` is invoked once

static orderBy(collection, iterateesopt, ordersopt) → {Array}

This method is like _.sortBy except that it allows specifying the sort
orders of the iteratees to sort by. If orders is unspecified, all values
are sorted in ascending order. Otherwise, specify an order of "desc" for
descending or "asc" for ascending sort order of corresponding values.

Parameters:
Name Type Attributes Default Description
collection Array | Object

The collection to iterate over.

iteratees Array.<Array> | Array.<function()> | Array.<Object> | Array.<string> <optional>
[_.identity]

The iteratees to sort by.

orders Array.<string> <optional>

The sort orders of iteratees.

Returns:
Array -

Returns the new sorted array.

Since:
  • 4.0.0
Example
var users = [
  { 'user': 'fred',   'age': 48 },
  { 'user': 'barney', 'age': 34 },
  { 'user': 'fred',   'age': 40 },
  { 'user': 'barney', 'age': 36 }
];

// Sort by `user` in ascending order and by `age` in descending order.
_.orderBy(users, ['user', 'age'], ['asc', 'desc']);
// => objects for [['barney', 36], ['barney', 34], ['fred', 48], ['fred', 40]]

static pad(stringopt, lengthopt, charsopt) → {string}

Pads string on the left and right sides if it's shorter than length.
Padding characters are truncated if they can't be evenly divided by length.

Parameters:
Name Type Attributes Default Description
string string <optional>
''

The string to pad.

length number <optional>
0

The padding length.

chars string <optional>
' '

The string used as padding.

Returns:
string -

Returns the padded string.

Since:
  • 3.0.0
Example
_.pad('abc', 8);
// => '  abc   '

_.pad('abc', 8, '_-');
// => '_-abc_-_'

_.pad('abc', 3);
// => 'abc'

static padEnd(stringopt, lengthopt, charsopt) → {string}

Pads string on the right side if it's shorter than length. Padding
characters are truncated if they exceed length.

Parameters:
Name Type Attributes Default Description
string string <optional>
''

The string to pad.

length number <optional>
0

The padding length.

chars string <optional>
' '

The string used as padding.

Returns:
string -

Returns the padded string.

Since:
  • 4.0.0
Example
_.padEnd('abc', 6);
// => 'abc   '

_.padEnd('abc', 6, '_-');
// => 'abc_-_'

_.padEnd('abc', 3);
// => 'abc'

static padStart(stringopt, lengthopt, charsopt) → {string}

Pads string on the left side if it's shorter than length. Padding
characters are truncated if they exceed length.

Parameters:
Name Type Attributes Default Description
string string <optional>
''

The string to pad.

length number <optional>
0

The padding length.

chars string <optional>
' '

The string used as padding.

Returns:
string -

Returns the padded string.

Since:
  • 4.0.0
Example
_.padStart('abc', 6);
// => '   abc'

_.padStart('abc', 6, '_-');
// => '_-_abc'

_.padStart('abc', 3);
// => 'abc'

static parseInt(string, radixopt) → {number}

Converts string to an integer of the specified radix. If radix is
undefined or 0, a radix of 10 is used unless value is a
hexadecimal, in which case a radix of 16 is used.

Note: This method aligns with the
ES5 implementation of parseInt.

Parameters:
Name Type Attributes Default Description
string string

The string to convert.

radix number <optional>
10

The radix to interpret value by.

Returns:
number -

Returns the converted integer.

Since:
  • 1.1.0
Example
_.parseInt('08');
// => 8

_.map(['6', '08', '10'], _.parseInt);
// => [6, 8, 10]

static pickBy(object, predicateopt) → {Object}

Creates an object composed of the object properties predicate returns
truthy for. The predicate is invoked with two arguments: (value, key).

Parameters:
Name Type Attributes Default Description
object Object

The source object.

predicate function <optional>
_.identity

The function invoked per property.

Returns:
Object -

Returns the new object.

Since:
  • 4.0.0
Example
var object = { 'a': 1, 'b': '2', 'c': 3 };

_.pickBy(object, _.isNumber);
// => { 'a': 1, 'c': 3 }

static property(path) → {function}

Creates a function that returns the value at path of a given object.

Parameters:
Name Type Description
path Array | string

The path of the property to get.

Returns:
function -

Returns the new accessor function.

Since:
  • 2.4.0
Example
var objects = [
  { 'a': { 'b': 2 } },
  { 'a': { 'b': 1 } }
];

_.map(objects, _.property('a.b'));
// => [2, 1]

_.map(_.sortBy(objects, _.property(['a', 'b'])), 'a.b');
// => [1, 2]

static propertyOf(object) → {function}

The opposite of _.property; this method creates a function that returns
the value at a given path of object.

Parameters:
Name Type Description
object Object

The object to query.

Returns:
function -

Returns the new accessor function.

Since:
  • 3.0.0
Example
var array = [0, 1, 2],
    object = { 'a': array, 'b': array, 'c': array };

_.map(['a[2]', 'c[0]'], _.propertyOf(object));
// => [2, 0]

_.map([['a', '2'], ['c', '0']], _.propertyOf(object));
// => [2, 0]

static pullAll(array, values) → {Array}

This method is like _.pull except that it accepts an array of values to remove.

Note: Unlike _.difference, this method mutates array.

Parameters:
Name Type Description
array Array

The array to modify.

values Array

The values to remove.

Returns:
Array -

Returns array.

Since:
  • 4.0.0
Example
var array = ['a', 'b', 'c', 'a', 'b', 'c'];

_.pullAll(array, ['a', 'c']);
console.log(array);
// => ['b', 'b']

static pullAllBy(array, values, iterateeopt) → {Array}

This method is like _.pullAll except that it accepts iteratee which is
invoked for each element of array and values to generate the criterion
by which they're compared. The iteratee is invoked with one argument: (value).

Note: Unlike _.differenceBy, this method mutates array.

Parameters:
Name Type Attributes Default Description
array Array

The array to modify.

values Array

The values to remove.

iteratee function <optional>
_.identity

The iteratee invoked per element.

Returns:
Array -

Returns array.

Since:
  • 4.0.0
Example
var array = [{ 'x': 1 }, { 'x': 2 }, { 'x': 3 }, { 'x': 1 }];

_.pullAllBy(array, [{ 'x': 1 }, { 'x': 3 }], 'x');
console.log(array);
// => [{ 'x': 2 }]

static pullAllWith(array, values, comparatoropt) → {Array}

This method is like _.pullAll except that it accepts comparator which
is invoked to compare elements of array to values. The comparator is
invoked with two arguments: (arrVal, othVal).

Note: Unlike _.differenceWith, this method mutates array.

Parameters:
Name Type Attributes Description
array Array

The array to modify.

values Array

The values to remove.

comparator function <optional>

The comparator invoked per element.

Returns:
Array -

Returns array.

Since:
  • 4.6.0
Example
var array = [{ 'x': 1, 'y': 2 }, { 'x': 3, 'y': 4 }, { 'x': 5, 'y': 6 }];

_.pullAllWith(array, [{ 'x': 3, 'y': 4 }], _.isEqual);
console.log(array);
// => [{ 'x': 1, 'y': 2 }, { 'x': 5, 'y': 6 }]

static random(loweropt, upperopt, floatingopt) → {number}

Produces a random number between the inclusive lower and upper bounds.
If only one argument is provided a number between 0 and the given number
is returned. If floating is true, or either lower or upper are
floats, a floating-point number is returned instead of an integer.

Note: JavaScript follows the IEEE-754 standard for resolving
floating-point values which can produce unexpected results.

Parameters:
Name Type Attributes Default Description
lower number <optional>
0

The lower bound.

upper number <optional>
1

The upper bound.

floating boolean <optional>

Specify returning a floating-point number.

Returns:
number -

Returns the random number.

Since:
  • 0.7.0
Example
_.random(0, 5);
// => an integer between 0 and 5

_.random(5);
// => also an integer between 0 and 5

_.random(5, true);
// => a floating-point number between 0 and 5

_.random(1.2, 5.2);
// => a floating-point number between 1.2 and 5.2

static reduce(collection, iterateeopt, accumulatoropt) → {*}

Reduces collection to a value which is the accumulated result of running
each element in collection thru iteratee, where each successive
invocation is supplied the return value of the previous. If accumulator
is not given, the first element of collection is used as the initial
value. The iteratee is invoked with four arguments:
(accumulator, value, index|key, collection).

Many lodash methods are guarded to work as iteratees for methods like
_.reduce, _.reduceRight, and _.transform.

The guarded methods are:
assign, defaults, defaultsDeep, includes, merge, orderBy,
and sortBy

Parameters:
Name Type Attributes Default Description
collection Array | Object

The collection to iterate over.

iteratee function <optional>
_.identity

The function invoked per iteration.

accumulator * <optional>

The initial value.

Returns:
* -

Returns the accumulated value.

Since:
  • 0.1.0
See:
Example
_.reduce([1, 2], function(sum, n) {
  return sum + n;
}, 0);
// => 3

_.reduce({ 'a': 1, 'b': 2, 'c': 1 }, function(result, value, key) {
  (result[value] || (result[value] = [])).push(key);
  return result;
}, {});
// => { '1': ['a', 'c'], '2': ['b'] } (iteration order is not guaranteed)

static reduceRight(collection, iterateeopt, accumulatoropt) → {*}

This method is like _.reduce except that it iterates over elements of
collection from right to left.

Parameters:
Name Type Attributes Default Description
collection Array | Object

The collection to iterate over.

iteratee function <optional>
_.identity

The function invoked per iteration.

accumulator * <optional>

The initial value.

Returns:
* -

Returns the accumulated value.

Since:
  • 0.1.0
See:
Example
var array = [[0, 1], [2, 3], [4, 5]];

_.reduceRight(array, function(flattened, other) {
  return flattened.concat(other);
}, []);
// => [4, 5, 2, 3, 0, 1]

static reject(collection, predicateopt) → {Array}

The opposite of _.filter; this method returns the elements of collection
that predicate does not return truthy for.

Parameters:
Name Type Attributes Default Description
collection Array | Object

The collection to iterate over.

predicate function <optional>
_.identity

The function invoked per iteration.

Returns:
Array -

Returns the new filtered array.

Since:
  • 0.1.0
See:
Example
var users = [
  { 'user': 'barney', 'age': 36, 'active': false },
  { 'user': 'fred',   'age': 40, 'active': true }
];

_.reject(users, function(o) { return !o.active; });
// => objects for ['fred']

// The `_.matches` iteratee shorthand.
_.reject(users, { 'age': 40, 'active': true });
// => objects for ['barney']

// The `_.matchesProperty` iteratee shorthand.
_.reject(users, ['active', false]);
// => objects for ['fred']

// The `_.property` iteratee shorthand.
_.reject(users, 'active');
// => objects for ['barney']

static remove(array, predicateopt) → {Array}

Removes all elements from array that predicate returns truthy for
and returns an array of the removed elements. The predicate is invoked
with three arguments: (value, index, array).

Note: Unlike _.filter, this method mutates array. Use _.pull
to pull elements from an array by value.

Parameters:
Name Type Attributes Default Description
array Array

The array to modify.

predicate function <optional>
_.identity

The function invoked per iteration.

Returns:
Array -

Returns the new array of removed elements.

Since:
  • 2.0.0
Example
var array = [1, 2, 3, 4];
var evens = _.remove(array, function(n) {
  return n % 2 == 0;
});

console.log(array);
// => [1, 3]

console.log(evens);
// => [2, 4]

static repeat(stringopt, nopt) → {string}

Repeats the given string n times.

Parameters:
Name Type Attributes Default Description
string string <optional>
''

The string to repeat.

n number <optional>
1

The number of times to repeat the string.

Returns:
string -

Returns the repeated string.

Since:
  • 3.0.0
Example
_.repeat('*', 3);
// => '***'

_.repeat('abc', 2);
// => 'abcabc'

_.repeat('abc', 0);
// => ''

static replace(stringopt, pattern, replacement) → {string}

Replaces matches for pattern in string with replacement.

Note: This method is based on
String#replace.

Parameters:
Name Type Attributes Default Description
string string <optional>
''

The string to modify.

pattern RegExp | string

The pattern to replace.

replacement function | string

The match replacement.

Returns:
string -

Returns the modified string.

Since:
  • 4.0.0
Example
_.replace('Hi Fred', 'Fred', 'Barney');
// => 'Hi Barney'

static rest(func, startopt) → {function}

Creates a function that invokes func with the this binding of the
created function and arguments from start and beyond provided as
an array.

Note: This method is based on the
rest parameter.

Parameters:
Name Type Attributes Default Description
func function

The function to apply a rest parameter to.

start number <optional>
func.length-1

The start position of the rest parameter.

Returns:
function -

Returns the new function.

Since:
  • 4.0.0
Example
var say = _.rest(function(what, names) {
  return what + ' ' + _.initial(names).join(', ') +
    (_.size(names) > 1 ? ', & ' : '') + _.last(names);
});

say('hello', 'fred', 'barney', 'pebbles');
// => 'hello fred, barney, & pebbles'

static result(object, path, defaultValueopt) → {*}

This method is like _.get except that if the resolved value is a
function it's invoked with the this binding of its parent object and
its result is returned.

Parameters:
Name Type Attributes Description
object Object

The object to query.

path Array | string

The path of the property to resolve.

defaultValue * <optional>

The value returned for undefined resolved values.

Returns:
* -

Returns the resolved value.

Since:
  • 0.1.0
Example
var object = { 'a': [{ 'b': { 'c1': 3, 'c2': _.constant(4) } }] };

_.result(object, 'a[0].b.c1');
// => 3

_.result(object, 'a[0].b.c2');
// => 4

_.result(object, 'a[0].b.c3', 'default');
// => 'default'

_.result(object, 'a[0].b.c3', _.constant('default'));
// => 'default'

static reverse(array) → {Array}

Reverses array so that the first element becomes the last, the second
element becomes the second to last, and so on.

Note: This method mutates array and is based on
Array#reverse.

Parameters:
Name Type Description
array Array

The array to modify.

Returns:
Array -

Returns array.

Since:
  • 4.0.0
Example
var array = [1, 2, 3];

_.reverse(array);
// => [3, 2, 1]

console.log(array);
// => [3, 2, 1]

static runInContext(contextopt) → {function}

Create a new pristine lodash function using the context object.

Parameters:
Name Type Attributes Default Description
context Object <optional>
root

The context object.

Returns:
function -

Returns a new lodash function.

Since:
  • 1.1.0
Example
_.mixin({ 'foo': _.constant('foo') });

var lodash = _.runInContext();
lodash.mixin({ 'bar': lodash.constant('bar') });

_.isFunction(_.foo);
// => true
_.isFunction(_.bar);
// => false

lodash.isFunction(lodash.foo);
// => false
lodash.isFunction(lodash.bar);
// => true

// Create a suped-up `defer` in Node.js.
var defer = _.runInContext({ 'setTimeout': setImmediate }).defer;

static sample(collection) → {*}

Gets a random element from collection.

Parameters:
Name Type Description
collection Array | Object

The collection to sample.

Returns:
* -

Returns the random element.

Since:
  • 2.0.0
Example
_.sample([1, 2, 3, 4]);
// => 2

static sampleSize(collection, nopt) → {Array}

Gets n random elements at unique keys from collection up to the
size of collection.

Parameters:
Name Type Attributes Default Description
collection Array | Object

The collection to sample.

n number <optional>
1

The number of elements to sample.

Returns:
Array -

Returns the random elements.

Since:
  • 4.0.0
Example
_.sampleSize([1, 2, 3], 2);
// => [3, 1]

_.sampleSize([1, 2, 3], 4);
// => [2, 3, 1]

static set(object, path, value) → {Object}

Sets the value at path of object. If a portion of path doesn't exist,
it's created. Arrays are created for missing index properties while objects
are created for all other missing properties. Use _.setWith to customize
path creation.

Note: This method mutates object.

Parameters:
Name Type Description
object Object

The object to modify.

path Array | string

The path of the property to set.

value *

The value to set.

Returns:
Object -

Returns object.

Since:
  • 3.7.0
Example
var object = { 'a': [{ 'b': { 'c': 3 } }] };

_.set(object, 'a[0].b.c', 4);
console.log(object.a[0].b.c);
// => 4

_.set(object, ['x', '0', 'y', 'z'], 5);
console.log(object.x[0].y.z);
// => 5

static setWith(object, path, value, customizeropt) → {Object}

This method is like _.set except that it accepts customizer which is
invoked to produce the objects of path. If customizer returns undefined
path creation is handled by the method instead. The customizer is invoked
with three arguments: (nsValue, key, nsObject).

Note: This method mutates object.

Parameters:
Name Type Attributes Description
object Object

The object to modify.

path Array | string

The path of the property to set.

value *

The value to set.

customizer function <optional>

The function to customize assigned values.

Returns:
Object -

Returns object.

Since:
  • 4.0.0
Example
var object = {};

_.setWith(object, '[0][1]', 'a', Object);
// => { '0': { '1': 'a' } }

static shuffle(collection) → {Array}

Creates an array of shuffled values, using a version of the
Fisher-Yates shuffle.

Parameters:
Name Type Description
collection Array | Object

The collection to shuffle.

Returns:
Array -

Returns the new shuffled array.

Since:
  • 0.1.0
Example
_.shuffle([1, 2, 3, 4]);
// => [4, 1, 3, 2]

static size(collection) → {number}

Gets the size of collection by returning its length for array-like
values or the number of own enumerable string keyed properties for objects.

Parameters:
Name Type Description
collection Array | Object | string

The collection to inspect.

Returns:
number -

Returns the collection size.

Since:
  • 0.1.0
Example
_.size([1, 2, 3]);
// => 3

_.size({ 'a': 1, 'b': 2 });
// => 2

_.size('pebbles');
// => 7

static slice(array, startopt, endopt) → {Array}

Creates a slice of array from start up to, but not including, end.

Note: This method is used instead of
Array#slice to ensure dense arrays are
returned.

Parameters:
Name Type Attributes Default Description
array Array

The array to slice.

start number <optional>
0

The start position.

end number <optional>
array.length

The end position.

Returns:
Array -

Returns the slice of array.

Since:
  • 3.0.0

static some(collection, predicateopt) → {boolean}

Checks if predicate returns truthy for any element of collection.
Iteration is stopped once predicate returns truthy. The predicate is
invoked with three arguments: (value, index|key, collection).

Parameters:
Name Type Attributes Default Description
collection Array | Object

The collection to iterate over.

predicate function <optional>
_.identity

The function invoked per iteration.

Returns:
boolean -

Returns true if any element passes the predicate check,
else false.

Since:
  • 0.1.0
Example
_.some([null, 0, 'yes', false], Boolean);
// => true

var users = [
  { 'user': 'barney', 'active': true },
  { 'user': 'fred',   'active': false }
];

// The `_.matches` iteratee shorthand.
_.some(users, { 'user': 'barney', 'active': false });
// => false

// The `_.matchesProperty` iteratee shorthand.
_.some(users, ['active', false]);
// => true

// The `_.property` iteratee shorthand.
_.some(users, 'active');
// => true

static sortedIndex(array, value) → {number}

Uses a binary search to determine the lowest index at which value
should be inserted into array in order to maintain its sort order.

Parameters:
Name Type Description
array Array

The sorted array to inspect.

value *

The value to evaluate.

Returns:
number -

Returns the index at which value should be inserted
into array.

Since:
  • 0.1.0
Example
_.sortedIndex([30, 50], 40);
// => 1

static sortedIndexBy(array, value, iterateeopt) → {number}

This method is like _.sortedIndex except that it accepts iteratee
which is invoked for value and each element of array to compute their
sort ranking. The iteratee is invoked with one argument: (value).

Parameters:
Name Type Attributes Default Description
array Array

The sorted array to inspect.

value *

The value to evaluate.

iteratee function <optional>
_.identity

The iteratee invoked per element.

Returns:
number -

Returns the index at which value should be inserted
into array.

Since:
  • 4.0.0
Example
var objects = [{ 'x': 4 }, { 'x': 5 }];

_.sortedIndexBy(objects, { 'x': 4 }, function(o) { return o.x; });
// => 0

// The `_.property` iteratee shorthand.
_.sortedIndexBy(objects, { 'x': 4 }, 'x');
// => 0

static sortedIndexOf(array, value) → {number}

This method is like _.indexOf except that it performs a binary
search on a sorted array.

Parameters:
Name Type Description
array Array

The array to inspect.

value *

The value to search for.

Returns:
number -

Returns the index of the matched value, else -1.

Since:
  • 4.0.0
Example
_.sortedIndexOf([4, 5, 5, 5, 6], 5);
// => 1

static sortedLastIndex(array, value) → {number}

This method is like _.sortedIndex except that it returns the highest
index at which value should be inserted into array in order to
maintain its sort order.

Parameters:
Name Type Description
array Array

The sorted array to inspect.

value *

The value to evaluate.

Returns:
number -

Returns the index at which value should be inserted
into array.

Since:
  • 3.0.0
Example
_.sortedLastIndex([4, 5, 5, 5, 6], 5);
// => 4

static sortedLastIndexBy(array, value, iterateeopt) → {number}

This method is like _.sortedLastIndex except that it accepts iteratee
which is invoked for value and each element of array to compute their
sort ranking. The iteratee is invoked with one argument: (value).

Parameters:
Name Type Attributes Default Description
array Array

The sorted array to inspect.

value *

The value to evaluate.

iteratee function <optional>
_.identity

The iteratee invoked per element.

Returns:
number -

Returns the index at which value should be inserted
into array.

Since:
  • 4.0.0
Example
var objects = [{ 'x': 4 }, { 'x': 5 }];

_.sortedLastIndexBy(objects, { 'x': 4 }, function(o) { return o.x; });
// => 1

// The `_.property` iteratee shorthand.
_.sortedLastIndexBy(objects, { 'x': 4 }, 'x');
// => 1

static sortedLastIndexOf(array, value) → {number}

This method is like _.lastIndexOf except that it performs a binary
search on a sorted array.

Parameters:
Name Type Description
array Array

The array to inspect.

value *

The value to search for.

Returns:
number -

Returns the index of the matched value, else -1.

Since:
  • 4.0.0
Example
_.sortedLastIndexOf([4, 5, 5, 5, 6], 5);
// => 3

static sortedUniq(array) → {Array}

This method is like _.uniq except that it's designed and optimized
for sorted arrays.

Parameters:
Name Type Description
array Array

The array to inspect.

Returns:
Array -

Returns the new duplicate free array.

Since:
  • 4.0.0
Example
_.sortedUniq([1, 1, 2]);
// => [1, 2]

static sortedUniqBy(array, iterateeopt) → {Array}

This method is like _.uniqBy except that it's designed and optimized
for sorted arrays.

Parameters:
Name Type Attributes Description
array Array

The array to inspect.

iteratee function <optional>

The iteratee invoked per element.

Returns:
Array -

Returns the new duplicate free array.

Since:
  • 4.0.0
Example
_.sortedUniqBy([1.1, 1.2, 2.3, 2.4], Math.floor);
// => [1.1, 2.3]

static split(stringopt, separator, limitopt) → {Array}

Splits string by separator.

Note: This method is based on
String#split.

Parameters:
Name Type Attributes Default Description
string string <optional>
''

The string to split.

separator RegExp | string

The separator pattern to split by.

limit number <optional>

The length to truncate results to.

Returns:
Array -

Returns the string segments.

Since:
  • 4.0.0
Example
_.split('a-b-c', '-', 2);
// => ['a', 'b']

static spread(func, startopt) → {function}

Creates a function that invokes func with the this binding of the
create function and an array of arguments much like
Function#apply.

Note: This method is based on the
spread operator.

Parameters:
Name Type Attributes Default Description
func function

The function to spread arguments over.

start number <optional>
0

The start position of the spread.

Returns:
function -

Returns the new function.

Since:
  • 3.2.0
Example
var say = _.spread(function(who, what) {
  return who + ' says ' + what;
});

say(['fred', 'hello']);
// => 'fred says hello'

var numbers = Promise.all([
  Promise.resolve(40),
  Promise.resolve(36)
]);

numbers.then(_.spread(function(x, y) {
  return x + y;
}));
// => a Promise of 76

static startsWith(stringopt, targetopt, positionopt) → {boolean}

Checks if string starts with the given target string.

Parameters:
Name Type Attributes Default Description
string string <optional>
''

The string to inspect.

target string <optional>

The string to search for.

position number <optional>
0

The position to search from.

Returns:
boolean -

Returns true if string starts with target,
else false.

Since:
  • 3.0.0
Example
_.startsWith('abc', 'a');
// => true

_.startsWith('abc', 'b');
// => false

_.startsWith('abc', 'b', 1);
// => true

static stubArray() → {Array}

This method returns a new empty array.

Returns:
Array -

Returns the new empty array.

Since:
  • 4.13.0
Example
var arrays = _.times(2, _.stubArray);

console.log(arrays);
// => [[], []]

console.log(arrays[0] === arrays[1]);
// => false

static stubFalse() → {boolean}

This method returns false.

Returns:
boolean -

Returns false.

Since:
  • 4.13.0
Example
_.times(2, _.stubFalse);
// => [false, false]

static stubObject() → {Object}

This method returns a new empty object.

Returns:
Object -

Returns the new empty object.

Since:
  • 4.13.0
Example
var objects = _.times(2, _.stubObject);

console.log(objects);
// => [{}, {}]

console.log(objects[0] === objects[1]);
// => false

static stubString() → {string}

This method returns an empty string.

Returns:
string -

Returns the empty string.

Since:
  • 4.13.0
Example
_.times(2, _.stubString);
// => ['', '']

static stubTrue() → {boolean}

This method returns true.

Returns:
boolean -

Returns true.

Since:
  • 4.13.0
Example
_.times(2, _.stubTrue);
// => [true, true]

static sum(array) → {number}

Computes the sum of the values in array.

Parameters:
Name Type Description
array Array

The array to iterate over.

Returns:
number -

Returns the sum.

Since:
  • 3.4.0
Example
_.sum([4, 2, 8, 6]);
// => 20

static sumBy(array, iterateeopt) → {number}

This method is like _.sum except that it accepts iteratee which is
invoked for each element in array to generate the value to be summed.
The iteratee is invoked with one argument: (value).

Parameters:
Name Type Attributes Default Description
array Array

The array to iterate over.

iteratee function <optional>
_.identity

The iteratee invoked per element.

Returns:
number -

Returns the sum.

Since:
  • 4.0.0
Example
var objects = [{ 'n': 4 }, { 'n': 2 }, { 'n': 8 }, { 'n': 6 }];

_.sumBy(objects, function(o) { return o.n; });
// => 20

// The `_.property` iteratee shorthand.
_.sumBy(objects, 'n');
// => 20

static tail(array) → {Array}

Gets all but the first element of array.

Parameters:
Name Type Description
array Array

The array to query.

Returns:
Array -

Returns the slice of array.

Since:
  • 4.0.0
Example
_.tail([1, 2, 3]);
// => [2, 3]

static take(array, nopt) → {Array}

Creates a slice of array with n elements taken from the beginning.

Parameters:
Name Type Attributes Default Description
array Array

The array to query.

n number <optional>
1

The number of elements to take.

Returns:
Array -

Returns the slice of array.

Since:
  • 0.1.0
Example
_.take([1, 2, 3]);
// => [1]

_.take([1, 2, 3], 2);
// => [1, 2]

_.take([1, 2, 3], 5);
// => [1, 2, 3]

_.take([1, 2, 3], 0);
// => []

static takeRight(array, nopt) → {Array}

Creates a slice of array with n elements taken from the end.

Parameters:
Name Type Attributes Default Description
array Array

The array to query.

n number <optional>
1

The number of elements to take.

Returns:
Array -

Returns the slice of array.

Since:
  • 3.0.0
Example
_.takeRight([1, 2, 3]);
// => [3]

_.takeRight([1, 2, 3], 2);
// => [2, 3]

_.takeRight([1, 2, 3], 5);
// => [1, 2, 3]

_.takeRight([1, 2, 3], 0);
// => []

static takeRightWhile(array, predicateopt) → {Array}

Creates a slice of array with elements taken from the end. Elements are
taken until predicate returns falsey. The predicate is invoked with
three arguments: (value, index, array).

Parameters:
Name Type Attributes Default Description
array Array

The array to query.

predicate function <optional>
_.identity

The function invoked per iteration.

Returns:
Array -

Returns the slice of array.

Since:
  • 3.0.0
Example
var users = [
  { 'user': 'barney',  'active': true },
  { 'user': 'fred',    'active': false },
  { 'user': 'pebbles', 'active': false }
];

_.takeRightWhile(users, function(o) { return !o.active; });
// => objects for ['fred', 'pebbles']

// The `_.matches` iteratee shorthand.
_.takeRightWhile(users, { 'user': 'pebbles', 'active': false });
// => objects for ['pebbles']

// The `_.matchesProperty` iteratee shorthand.
_.takeRightWhile(users, ['active', false]);
// => objects for ['fred', 'pebbles']

// The `_.property` iteratee shorthand.
_.takeRightWhile(users, 'active');
// => []

static takeWhile(array, predicateopt) → {Array}

Creates a slice of array with elements taken from the beginning. Elements
are taken until predicate returns falsey. The predicate is invoked with
three arguments: (value, index, array).

Parameters:
Name Type Attributes Default Description
array Array

The array to query.

predicate function <optional>
_.identity

The function invoked per iteration.

Returns:
Array -

Returns the slice of array.

Since:
  • 3.0.0
Example
var users = [
  { 'user': 'barney',  'active': false },
  { 'user': 'fred',    'active': false },
  { 'user': 'pebbles', 'active': true }
];

_.takeWhile(users, function(o) { return !o.active; });
// => objects for ['barney', 'fred']

// The `_.matches` iteratee shorthand.
_.takeWhile(users, { 'user': 'barney', 'active': false });
// => objects for ['barney']

// The `_.matchesProperty` iteratee shorthand.
_.takeWhile(users, ['active', false]);
// => objects for ['barney', 'fred']

// The `_.property` iteratee shorthand.
_.takeWhile(users, 'active');
// => []

static tap(value, interceptor) → {*}

This method invokes interceptor and returns value. The interceptor
is invoked with one argument; (value). The purpose of this method is to
"tap into" a method chain sequence in order to modify intermediate results.

Parameters:
Name Type Description
value *

The value to provide to interceptor.

interceptor function

The function to invoke.

Returns:
* -

Returns value.

Since:
  • 0.1.0
Example
_([1, 2, 3])
 .tap(function(array) {
   // Mutate input array.
   array.pop();
 })
 .reverse()
 .value();
// => [2, 1]

static template(stringopt, optionsopt) → {function}

Creates a compiled template function that can interpolate data properties
in "interpolate" delimiters, HTML-escape interpolated data properties in
"escape" delimiters, and execute JavaScript in "evaluate" delimiters. Data
properties may be accessed as free variables in the template. If a setting
object is given, it takes precedence over _.templateSettings values.

Note: In the development build _.template utilizes
sourceURLs
for easier debugging.

For more information on precompiling templates see
lodash's custom builds documentation.

For more information on Chrome extension sandboxes see
Chrome's extensions documentation.

Parameters:
Name Type Attributes Default Description
string string <optional>
''

The template string.

options Object <optional>
{}

The options object.

Properties
Name Type Attributes Default Description
escape RegExp <optional>
_.templateSettings.escape

The HTML "escape" delimiter.

evaluate RegExp <optional>
_.templateSettings.evaluate

The "evaluate" delimiter.

imports Object <optional>
_.templateSettings.imports

An object to import into the template as free variables.

interpolate RegExp <optional>
_.templateSettings.interpolate

The "interpolate" delimiter.

sourceURL string <optional>
'lodash.templateSources[n]'

The sourceURL of the compiled template.

variable string <optional>
'obj'

The data object variable name.

Returns:
function -

Returns the compiled template function.

Since:
  • 0.1.0
Example
// Use the "interpolate" delimiter to create a compiled template.
var compiled = _.template('hello <%= user %>!');
compiled({ 'user': 'fred' });
// => 'hello fred!'

// Use the HTML "escape" delimiter to escape data property values.
var compiled = _.template('<b><%- value %></b>');
compiled({ 'value': '<script>' });
// => '<b>&lt;script&gt;</b>'

// Use the "evaluate" delimiter to execute JavaScript and generate HTML.
var compiled = _.template('<% _.forEach(users, function(user) { %><li><%- user %></li><% }); %>');
compiled({ 'users': ['fred', 'barney'] });
// => '<li>fred</li><li>barney</li>'

// Use the internal `print` function in "evaluate" delimiters.
var compiled = _.template('<% print("hello " + user); %>!');
compiled({ 'user': 'barney' });
// => 'hello barney!'

// Use the ES template literal delimiter as an "interpolate" delimiter.
// Disable support by replacing the "interpolate" delimiter.
var compiled = _.template('hello ${ user }!');
compiled({ 'user': 'pebbles' });
// => 'hello pebbles!'

// Use backslashes to treat delimiters as plain text.
var compiled = _.template('<%= "\\<%- value %\\>" %>');
compiled({ 'value': 'ignored' });
// => '<%- value %>'

// Use the `imports` option to import `jQuery` as `jq`.
var text = '<% jq.each(users, function(user) { %><li><%- user %></li><% }); %>';
var compiled = _.template(text, { 'imports': { 'jq': jQuery } });
compiled({ 'users': ['fred', 'barney'] });
// => '<li>fred</li><li>barney</li>'

// Use the `sourceURL` option to specify a custom sourceURL for the template.
var compiled = _.template('hello <%= user %>!', { 'sourceURL': '/basic/greeting.jst' });
compiled(data);
// => Find the source of "greeting.jst" under the Sources tab or Resources panel of the web inspector.

// Use the `variable` option to ensure a with-statement isn't used in the compiled template.
var compiled = _.template('hi <%= data.user %>!', { 'variable': 'data' });
compiled.source;
// => function(data) {
//   var __t, __p = '';
//   __p += 'hi ' + ((__t = ( data.user )) == null ? '' : __t) + '!';
//   return __p;
// }

// Use custom template delimiters.
_.templateSettings.interpolate = /{{([\s\S]+?)}}/g;
var compiled = _.template('hello {{ user }}!');
compiled({ 'user': 'mustache' });
// => 'hello mustache!'

// Use the `source` property to inline compiled templates for meaningful
// line numbers in error messages and stack traces.
fs.writeFileSync(path.join(process.cwd(), 'jst.js'), '\
  var JST = {\
    "main": ' + _.template(mainText).source + '\
  };\
');

static throttle(func, waitopt, optionsopt) → {function}

Creates a throttled function that only invokes func at most once per
every wait milliseconds. The throttled function comes with a cancel
method to cancel delayed func invocations and a flush method to
immediately invoke them. Provide options to indicate whether func
should be invoked on the leading and/or trailing edge of the wait
timeout. The func is invoked with the last arguments provided to the
throttled function. Subsequent calls to the throttled function return the
result of the last func invocation.

Note: If leading and trailing options are true, func is
invoked on the trailing edge of the timeout only if the throttled function
is invoked more than once during the wait timeout.

If wait is 0 and leading is false, func invocation is deferred
until to the next tick, similar to setTimeout with a timeout of 0.

See David Corbacho's article
for details over the differences between _.throttle and _.debounce.

Parameters:
Name Type Attributes Default Description
func function

The function to throttle.

wait number <optional>
0

The number of milliseconds to throttle invocations to.

options Object <optional>
{}

The options object.

Properties
Name Type Attributes Default Description
leading boolean <optional>
true

Specify invoking on the leading edge of the timeout.

trailing boolean <optional>
true

Specify invoking on the trailing edge of the timeout.

Returns:
function -

Returns the new throttled function.

Since:
  • 0.1.0
Example
// Avoid excessively updating the position while scrolling.
jQuery(window).on('scroll', _.throttle(updatePosition, 100));

// Invoke `renewToken` when the click event is fired, but not more than once every 5 minutes.
var throttled = _.throttle(renewToken, 300000, { 'trailing': false });
jQuery(element).on('click', throttled);

// Cancel the trailing throttled invocation.
jQuery(window).on('popstate', throttled.cancel);

static thru(value, interceptor) → {*}

This method is like _.tap except that it returns the result of interceptor.
The purpose of this method is to "pass thru" values replacing intermediate
results in a method chain sequence.

Parameters:
Name Type Description
value *

The value to provide to interceptor.

interceptor function

The function to invoke.

Returns:
* -

Returns the result of interceptor.

Since:
  • 3.0.0
Example
_('  abc  ')
 .chain()
 .trim()
 .thru(function(value) {
   return [value];
 })
 .value();
// => ['abc']

static times(n, iterateeopt) → {Array}

Invokes the iteratee n times, returning an array of the results of
each invocation. The iteratee is invoked with one argument; (index).

Parameters:
Name Type Attributes Default Description
n number

The number of times to invoke iteratee.

iteratee function <optional>
_.identity

The function invoked per iteration.

Returns:
Array -

Returns the array of results.

Since:
  • 0.1.0
Example
_.times(3, String);
// => ['0', '1', '2']

 _.times(4, _.constant(0));
// => [0, 0, 0, 0]

static toArray(value) → {Array}

Converts value to an array.

Parameters:
Name Type Description
value *

The value to convert.

Returns:
Array -

Returns the converted array.

Since:
  • 0.1.0
Example
_.toArray({ 'a': 1, 'b': 2 });
// => [1, 2]

_.toArray('abc');
// => ['a', 'b', 'c']

_.toArray(1);
// => []

_.toArray(null);
// => []

static toFinite(value) → {number}

Converts value to a finite number.

Parameters:
Name Type Description
value *

The value to convert.

Returns:
number -

Returns the converted number.

Since:
  • 4.12.0
Example
_.toFinite(3.2);
// => 3.2

_.toFinite(Number.MIN_VALUE);
// => 5e-324

_.toFinite(Infinity);
// => 1.7976931348623157e+308

_.toFinite('3.2');
// => 3.2

static toInteger(value) → {number}

Converts value to an integer.

Note: This method is loosely based on
ToInteger.

Parameters:
Name Type Description
value *

The value to convert.

Returns:
number -

Returns the converted integer.

Since:
  • 4.0.0
Example
_.toInteger(3.2);
// => 3

_.toInteger(Number.MIN_VALUE);
// => 0

_.toInteger(Infinity);
// => 1.7976931348623157e+308

_.toInteger('3.2');
// => 3

static toLength(value) → {number}

Converts value to an integer suitable for use as the length of an
array-like object.

Note: This method is based on
ToLength.

Parameters:
Name Type Description
value *

The value to convert.

Returns:
number -

Returns the converted integer.

Since:
  • 4.0.0
Example
_.toLength(3.2);
// => 3

_.toLength(Number.MIN_VALUE);
// => 0

_.toLength(Infinity);
// => 4294967295

_.toLength('3.2');
// => 3

static toLower(stringopt) → {string}

Converts string, as a whole, to lower case just like
String#toLowerCase.

Parameters:
Name Type Attributes Default Description
string string <optional>
''

The string to convert.

Returns:
string -

Returns the lower cased string.

Since:
  • 4.0.0
Example
_.toLower('--Foo-Bar--');
// => '--foo-bar--'

_.toLower('fooBar');
// => 'foobar'

_.toLower('__FOO_BAR__');
// => '__foo_bar__'

static toNumber(value) → {number}

Converts value to a number.

Parameters:
Name Type Description
value *

The value to process.

Returns:
number -

Returns the number.

Since:
  • 4.0.0
Example
_.toNumber(3.2);
// => 3.2

_.toNumber(Number.MIN_VALUE);
// => 5e-324

_.toNumber(Infinity);
// => Infinity

_.toNumber('3.2');
// => 3.2

static toPath(value) → {Array}

Converts value to a property path array.

Parameters:
Name Type Description
value *

The value to convert.

Returns:
Array -

Returns the new property path array.

Since:
  • 4.0.0
Example
_.toPath('a.b.c');
// => ['a', 'b', 'c']

_.toPath('a[0].b.c');
// => ['a', '0', 'b', 'c']

static toPlainObject(value) → {Object}

Converts value to a plain object flattening inherited enumerable string
keyed properties of value to own properties of the plain object.

Parameters:
Name Type Description
value *

The value to convert.

Returns:
Object -

Returns the converted plain object.

Since:
  • 3.0.0
Example
function Foo() {
  this.b = 2;
}

Foo.prototype.c = 3;

_.assign({ 'a': 1 }, new Foo);
// => { 'a': 1, 'b': 2 }

_.assign({ 'a': 1 }, _.toPlainObject(new Foo));
// => { 'a': 1, 'b': 2, 'c': 3 }

static toSafeInteger(value) → {number}

Converts value to a safe integer. A safe integer can be compared and
represented correctly.

Parameters:
Name Type Description
value *

The value to convert.

Returns:
number -

Returns the converted integer.

Since:
  • 4.0.0
Example
_.toSafeInteger(3.2);
// => 3

_.toSafeInteger(Number.MIN_VALUE);
// => 0

_.toSafeInteger(Infinity);
// => 9007199254740991

_.toSafeInteger('3.2');
// => 3

static toString(value) → {string}

Converts value to a string. An empty string is returned for null
and undefined values. The sign of -0 is preserved.

Parameters:
Name Type Description
value *

The value to convert.

Returns:
string -

Returns the converted string.

Since:
  • 4.0.0
Example
_.toString(null);
// => ''

_.toString(-0);
// => '-0'

_.toString([1, 2, 3]);
// => '1,2,3'

static toUpper(stringopt) → {string}

Converts string, as a whole, to upper case just like
String#toUpperCase.

Parameters:
Name Type Attributes Default Description
string string <optional>
''

The string to convert.

Returns:
string -

Returns the upper cased string.

Since:
  • 4.0.0
Example
_.toUpper('--foo-bar--');
// => '--FOO-BAR--'

_.toUpper('fooBar');
// => 'FOOBAR'

_.toUpper('__foo_bar__');
// => '__FOO_BAR__'

static transform(object, iterateeopt, accumulatoropt) → {*}

An alternative to _.reduce; this method transforms object to a new
accumulator object which is the result of running each of its own
enumerable string keyed properties thru iteratee, with each invocation
potentially mutating the accumulator object. If accumulator is not
provided, a new object with the same [[Prototype]] will be used. The
iteratee is invoked with four arguments: (accumulator, value, key, object).
Iteratee functions may exit iteration early by explicitly returning false.

Parameters:
Name Type Attributes Default Description
object Object

The object to iterate over.

iteratee function <optional>
_.identity

The function invoked per iteration.

accumulator * <optional>

The custom accumulator value.

Returns:
* -

Returns the accumulated value.

Since:
  • 1.3.0
Example
_.transform([2, 3, 4], function(result, n) {
  result.push(n *= n);
  return n % 2 == 0;
}, []);
// => [4, 9]

_.transform({ 'a': 1, 'b': 2, 'c': 1 }, function(result, value, key) {
  (result[value] || (result[value] = [])).push(key);
}, {});
// => { '1': ['a', 'c'], '2': ['b'] }

static trim(stringopt, charsopt) → {string}

Removes leading and trailing whitespace or specified characters from string.

Parameters:
Name Type Attributes Default Description
string string <optional>
''

The string to trim.

chars string <optional>
whitespace

The characters to trim.

Returns:
string -

Returns the trimmed string.

Since:
  • 3.0.0
Example
_.trim('  abc  ');
// => 'abc'

_.trim('-_-abc-_-', '_-');
// => 'abc'

_.map(['  foo  ', '  bar  '], _.trim);
// => ['foo', 'bar']

static trimEnd(stringopt, charsopt) → {string}

Removes trailing whitespace or specified characters from string.

Parameters:
Name Type Attributes Default Description
string string <optional>
''

The string to trim.

chars string <optional>
whitespace

The characters to trim.

Returns:
string -

Returns the trimmed string.

Since:
  • 4.0.0
Example
_.trimEnd('  abc  ');
// => '  abc'

_.trimEnd('-_-abc-_-', '_-');
// => '-_-abc'

static trimStart(stringopt, charsopt) → {string}

Removes leading whitespace or specified characters from string.

Parameters:
Name Type Attributes Default Description
string string <optional>
''

The string to trim.

chars string <optional>
whitespace

The characters to trim.

Returns:
string -

Returns the trimmed string.

Since:
  • 4.0.0
Example
_.trimStart('  abc  ');
// => 'abc  '

_.trimStart('-_-abc-_-', '_-');
// => 'abc-_-'

static truncate(stringopt, optionsopt) → {string}

Truncates string if it's longer than the given maximum string length.
The last characters of the truncated string are replaced with the omission
string which defaults to "...".

Parameters:
Name Type Attributes Default Description
string string <optional>
''

The string to truncate.

options Object <optional>
{}

The options object.

Properties
Name Type Attributes Default Description
length number <optional>
30

The maximum string length.

omission string <optional>
'...'

The string to indicate text is omitted.

separator RegExp | string <optional>

The separator pattern to truncate to.

Returns:
string -

Returns the truncated string.

Since:
  • 4.0.0
Example
_.truncate('hi-diddly-ho there, neighborino');
// => 'hi-diddly-ho there, neighbo...'

_.truncate('hi-diddly-ho there, neighborino', {
  'length': 24,
  'separator': ' '
});
// => 'hi-diddly-ho there,...'

_.truncate('hi-diddly-ho there, neighborino', {
  'length': 24,
  'separator': /,? +/
});
// => 'hi-diddly-ho there...'

_.truncate('hi-diddly-ho there, neighborino', {
  'omission': ' [...]'
});
// => 'hi-diddly-ho there, neig [...]'

static unary(func) → {function}

Creates a function that accepts up to one argument, ignoring any
additional arguments.

Parameters:
Name Type Description
func function

The function to cap arguments for.

Returns:
function -

Returns the new capped function.

Since:
  • 4.0.0
Example
_.map(['6', '8', '10'], _.unary(parseInt));
// => [6, 8, 10]

static unescape(stringopt) → {string}

The inverse of _.escape; this method converts the HTML entities
&amp;, &lt;, &gt;, &quot;, and &#39; in string to
their corresponding characters.

Note: No other HTML entities are unescaped. To unescape additional
HTML entities use a third-party library like he.

Parameters:
Name Type Attributes Default Description
string string <optional>
''

The string to unescape.

Returns:
string -

Returns the unescaped string.

Since:
  • 0.6.0
Example
_.unescape('fred, barney, &amp; pebbles');
// => 'fred, barney, & pebbles'

static uniq(array) → {Array}

Creates a duplicate-free version of an array, using
SameValueZero
for equality comparisons, in which only the first occurrence of each element
is kept. The order of result values is determined by the order they occur
in the array.

Parameters:
Name Type Description
array Array

The array to inspect.

Returns:
Array -

Returns the new duplicate free array.

Since:
  • 0.1.0
Example
_.uniq([2, 1, 2]);
// => [2, 1]

static uniqBy(array, iterateeopt) → {Array}

This method is like _.uniq except that it accepts iteratee which is
invoked for each element in array to generate the criterion by which
uniqueness is computed. The order of result values is determined by the
order they occur in the array. The iteratee is invoked with one argument:
(value).

Parameters:
Name Type Attributes Default Description
array Array

The array to inspect.

iteratee function <optional>
_.identity

The iteratee invoked per element.

Returns:
Array -

Returns the new duplicate free array.

Since:
  • 4.0.0
Example
_.uniqBy([2.1, 1.2, 2.3], Math.floor);
// => [2.1, 1.2]

// The `_.property` iteratee shorthand.
_.uniqBy([{ 'x': 1 }, { 'x': 2 }, { 'x': 1 }], 'x');
// => [{ 'x': 1 }, { 'x': 2 }]

static uniqWith(array, comparatoropt) → {Array}

This method is like _.uniq except that it accepts comparator which
is invoked to compare elements of array. The order of result values is
determined by the order they occur in the array.The comparator is invoked
with two arguments: (arrVal, othVal).

Parameters:
Name Type Attributes Description
array Array

The array to inspect.

comparator function <optional>

The comparator invoked per element.

Returns:
Array -

Returns the new duplicate free array.

Since:
  • 4.0.0
Example
var objects = [{ 'x': 1, 'y': 2 }, { 'x': 2, 'y': 1 }, { 'x': 1, 'y': 2 }];

_.uniqWith(objects, _.isEqual);
// => [{ 'x': 1, 'y': 2 }, { 'x': 2, 'y': 1 }]

static uniqueId(prefixopt) → {string}

Generates a unique ID. If prefix is given, the ID is appended to it.

Parameters:
Name Type Attributes Default Description
prefix string <optional>
''

The value to prefix the ID with.

Returns:
string -

Returns the unique ID.

Since:
  • 0.1.0
Example
_.uniqueId('contact_');
// => 'contact_104'

_.uniqueId();
// => '105'

static unset(object, path) → {boolean}

Removes the property at path of object.

Note: This method mutates object.

Parameters:
Name Type Description
object Object

The object to modify.

path Array | string

The path of the property to unset.

Returns:
boolean -

Returns true if the property is deleted, else false.

Since:
  • 4.0.0
Example
var object = { 'a': [{ 'b': { 'c': 7 } }] };
_.unset(object, 'a[0].b.c');
// => true

console.log(object);
// => { 'a': [{ 'b': {} }] };

_.unset(object, ['a', '0', 'b', 'c']);
// => true

console.log(object);
// => { 'a': [{ 'b': {} }] };

static unzip(array) → {Array}

This method is like _.zip except that it accepts an array of grouped
elements and creates an array regrouping the elements to their pre-zip
configuration.

Parameters:
Name Type Description
array Array

The array of grouped elements to process.

Returns:
Array -

Returns the new array of regrouped elements.

Since:
  • 1.2.0
Example
var zipped = _.zip(['a', 'b'], [1, 2], [true, false]);
// => [['a', 1, true], ['b', 2, false]]

_.unzip(zipped);
// => [['a', 'b'], [1, 2], [true, false]]

static unzipWith(array, iterateeopt) → {Array}

This method is like _.unzip except that it accepts iteratee to specify
how regrouped values should be combined. The iteratee is invoked with the
elements of each group: (...group).

Parameters:
Name Type Attributes Default Description
array Array

The array of grouped elements to process.

iteratee function <optional>
_.identity

The function to combine
regrouped values.

Returns:
Array -

Returns the new array of regrouped elements.

Since:
  • 3.8.0
Example
var zipped = _.zip([1, 2], [10, 20], [100, 200]);
// => [[1, 10, 100], [2, 20, 200]]

_.unzipWith(zipped, _.add);
// => [3, 30, 300]

static update(object, path, updater) → {Object}

This method is like _.set except that accepts updater to produce the
value to set. Use _.updateWith to customize path creation. The updater
is invoked with one argument: (value).

Note: This method mutates object.

Parameters:
Name Type Description
object Object

The object to modify.

path Array | string

The path of the property to set.

updater function

The function to produce the updated value.

Returns:
Object -

Returns object.

Since:
  • 4.6.0
Example
var object = { 'a': [{ 'b': { 'c': 3 } }] };

_.update(object, 'a[0].b.c', function(n) { return n * n; });
console.log(object.a[0].b.c);
// => 9

_.update(object, 'x[0].y.z', function(n) { return n ? n + 1 : 0; });
console.log(object.x[0].y.z);
// => 0

static updateWith(object, path, updater, customizeropt) → {Object}

This method is like _.update except that it accepts customizer which is
invoked to produce the objects of path. If customizer returns undefined
path creation is handled by the method instead. The customizer is invoked
with three arguments: (nsValue, key, nsObject).

Note: This method mutates object.

Parameters:
Name Type Attributes Description
object Object

The object to modify.

path Array | string

The path of the property to set.

updater function

The function to produce the updated value.

customizer function <optional>

The function to customize assigned values.

Returns:
Object -

Returns object.

Since:
  • 4.6.0
Example
var object = {};

_.updateWith(object, '[0][1]', _.constant('a'), Object);
// => { '0': { '1': 'a' } }

static values(object) → {Array}

Creates an array of the own enumerable string keyed property values of object.

Note: Non-object values are coerced to objects.

Parameters:
Name Type Description
object Object

The object to query.

Returns:
Array -

Returns the array of property values.

Since:
  • 0.1.0
Example
function Foo() {
  this.a = 1;
  this.b = 2;
}

Foo.prototype.c = 3;

_.values(new Foo);
// => [1, 2] (iteration order is not guaranteed)

_.values('hi');
// => ['h', 'i']

static valuesIn(object) → {Array}

Creates an array of the own and inherited enumerable string keyed property
values of object.

Note: Non-object values are coerced to objects.

Parameters:
Name Type Description
object Object

The object to query.

Returns:
Array -

Returns the array of property values.

Since:
  • 3.0.0
Example
function Foo() {
  this.a = 1;
  this.b = 2;
}

Foo.prototype.c = 3;

_.valuesIn(new Foo);
// => [1, 2, 3] (iteration order is not guaranteed)

static words(stringopt, patternopt) → {Array}

Splits string into an array of its words.

Parameters:
Name Type Attributes Default Description
string string <optional>
''

The string to inspect.

pattern RegExp | string <optional>

The pattern to match words.

Returns:
Array -

Returns the words of string.

Since:
  • 3.0.0
Example
_.words('fred, barney, & pebbles');
// => ['fred', 'barney', 'pebbles']

_.words('fred, barney, & pebbles', /[^, ]+/g);
// => ['fred', 'barney', '&', 'pebbles']

static wrap(value, wrapperopt) → {function}

Creates a function that provides value to wrapper as its first
argument. Any additional arguments provided to the function are appended
to those provided to the wrapper. The wrapper is invoked with the this
binding of the created function.

Parameters:
Name Type Attributes Default Description
value *

The value to wrap.

wrapper function <optional>
identity

The wrapper function.

Returns:
function -

Returns the new function.

Since:
  • 0.1.0
Example
var p = _.wrap(_.escape, function(func, text) {
  return '<p>' + func(text) + '</p>';
});

p('fred, barney, & pebbles');
// => '<p>fred, barney, &amp; pebbles</p>'

static zipObject(propsopt, valuesopt) → {Object}

This method is like _.fromPairs except that it accepts two arrays,
one of property identifiers and one of corresponding values.

Parameters:
Name Type Attributes Default Description
props Array <optional>
[]

The property identifiers.

values Array <optional>
[]

The property values.

Returns:
Object -

Returns the new object.

Since:
  • 0.4.0
Example
_.zipObject(['a', 'b'], [1, 2]);
// => { 'a': 1, 'b': 2 }

static zipObjectDeep(propsopt, valuesopt) → {Object}

This method is like _.zipObject except that it supports property paths.

Parameters:
Name Type Attributes Default Description
props Array <optional>
[]

The property identifiers.

values Array <optional>
[]

The property values.

Returns:
Object -

Returns the new object.

Since:
  • 4.1.0
Example
_.zipObjectDeep(['a.b[0].c', 'a.b[1].d'], [1, 2]);
// => { 'a': { 'b': [{ 'c': 1 }, { 'd': 2 }] } }