147 KiB
Lo-Dash v2.4.2
Arrays
_.compact_.difference_.drop->rest_.findIndex_.findLastIndex_.first_.flatten_.head->first_.indexOf_.initial_.intersection_.last_.lastIndexOf_.object->zipObject_.pull_.range_.remove_.rest_.sortedIndex_.tail->rest_.take->first_.union_.uniq_.unique->uniq_.unzip->zip_.without_.xor_.zip_.zipObject
Chaining
__.chain_.tap_.prototype.chain_.prototype.toString_.prototype.value->valueOf_.prototype.valueOf
Collections
_.all->every_.any->some_.at_.collect->map_.contains_.countBy_.detect->find_.each->forEach_.eachRight->forEachRight_.every_.filter_.find_.findLast_.findWhere->find_.foldl->reduce_.foldr->reduceRight_.forEach_.forEachRight_.groupBy_.include->contains_.indexBy_.inject->reduce_.invoke_.map_.max_.min_.pluck_.reduce_.reduceRight_.reject_.sample_.select->filter_.shuffle_.size_.some_.sortBy_.toArray_.where
Functions
_.after_.bind_.bindAll_.bindKey_.compose_.curry_.debounce_.defer_.delay_.memoize_.once_.partial_.partialRight_.throttle_.wrap
Objects
_.assign_.clone_.cloneDeep_.create_.defaults_.extend->assign_.findKey_.findLastKey_.forIn_.forInRight_.forOwn_.forOwnRight_.functions_.has_.invert_.isArguments_.isArray_.isBoolean_.isDate_.isElement_.isEmpty_.isEqual_.isFinite_.isFunction_.isNaN_.isNull_.isNumber_.isObject_.isPlainObject_.isRegExp_.isString_.isUndefined_.keys_.mapValues_.merge_.methods->functions_.omit_.pairs_.pick_.transform_.values
Utilities
_.constant_.createCallback_.escape_.identity_.mixin_.noConflict_.noop_.now_.parseInt_.property_.random_.result_.runInContext_.template_.times_.unescape_.uniqueId
Methods
Properties
_.VERSION_.support_.support.argsClass_.support.argsObject_.support.enumErrorProps_.support.enumPrototypes_.support.funcDecomp_.support.funcNames_.support.nonEnumArgs_.support.nonEnumShadows_.support.ownLast_.support.spliceObjects_.support.unindexedChars_.templateSettings_.templateSettings.escape_.templateSettings.evaluate_.templateSettings.imports_.templateSettings.interpolate_.templateSettings.variable
“Arrays” Methods
_.compact(array)
Creates an array with all falsey values removed. The values false, null,
0, "", undefined, and NaN are all falsey.
Arguments
array(Array): The array to compact.
Returns
(Array): Returns a new array of filtered values.
Example
_.compact([0, 1, false, 2, '', 3]);
// => [1, 2, 3]
_.difference(array, [values])
Creates an array excluding all values of the provided arrays using strict
equality for comparisons, i.e. ===.
Arguments
array(Array): The array to process.[values](...Array): The arrays of values to exclude.
Returns
(Array): Returns a new array of filtered values.
Example
_.difference([1, 2, 3, 4, 5], [5, 2, 10]);
// => [1, 3, 4]
_.findIndex(array, [callback=identity], [thisArg])
This method is like _.find except that it returns the index of the first
element that passes the callback check, instead of the element itself.
If a property name is provided for callback the created ".pluck" style
callback will return the property value of the given element.
If an object is provided for callback the created ".where" style callback
will return true for elements that have the properties of the given object,
else false.
Arguments
array(Array): The array to search.[callback=identity](Function|Object|string): The function called per iteration. If a property name or object is provided it will be used to create a ".pluck" or ".where" style callback, respectively.[thisArg](*): Thethisbinding ofcallback.
Returns
(number): Returns the index of the found element, else -1.
Example
var characters = [
{ 'name': 'barney', 'age': 36, 'blocked': false },
{ 'name': 'fred', 'age': 40, 'blocked': true },
{ 'name': 'pebbles', 'age': 1, 'blocked': false }
];
_.findIndex(characters, function(chr) {
return chr.age < 20;
});
// => 2
// using "_.where" callback shorthand
_.findIndex(characters, { 'age': 36 });
// => 0
// using "_.pluck" callback shorthand
_.findIndex(characters, 'blocked');
// => 1
_.findLastIndex(array, [callback=identity], [thisArg])
This method is like _.findIndex except that it iterates over elements
of a collection from right to left.
If a property name is provided for callback the created ".pluck" style
callback will return the property value of the given element.
If an object is provided for callback the created ".where" style callback
will return true for elements that have the properties of the given object,
else false.
Arguments
array(Array): The array to search.[callback=identity](Function|Object|string): The function called per iteration. If a property name or object is provided it will be used to create a ".pluck" or ".where" style callback, respectively.[thisArg](*): Thethisbinding ofcallback.
Returns
(number): Returns the index of the found element, else -1.
Example
var characters = [
{ 'name': 'barney', 'age': 36, 'blocked': true },
{ 'name': 'fred', 'age': 40, 'blocked': false },
{ 'name': 'pebbles', 'age': 1, 'blocked': true }
];
_.findLastIndex(characters, function(chr) {
return chr.age > 30;
});
// => 1
// using "_.where" callback shorthand
_.findLastIndex(characters, { 'age': 36 });
// => 0
// using "_.pluck" callback shorthand
_.findLastIndex(characters, 'blocked');
// => 2
_.first(array, [callback], [thisArg])
Gets the first element or first n elements of an array. If a callback
is provided elements at the beginning of the array are returned as long
as the callback returns truey. The callback is bound to thisArg and
invoked with three arguments; (value, index, array).
If a property name is provided for callback the created ".pluck" style
callback will return the property value of the given element.
If an object is provided for callback the created ".where" style callback
will return true for elements that have the properties of the given object,
else false.
Aliases
_.head, _.take
Arguments
array(Array): The array to query.[callback](Function|Object|number|string): The function called per element or the number of elements to return. If a property name or object is provided it will be used to create a ".pluck" or ".where" style callback, respectively.[thisArg](*): Thethisbinding ofcallback.
Returns
(*): Returns the first element(s) of array.
Example
_.first([1, 2, 3]);
// => 1
_.first([1, 2, 3], 2);
// => [1, 2]
_.first([1, 2, 3], function(num) {
return num < 3;
});
// => [1, 2]
var characters = [
{ 'name': 'barney', 'blocked': true, 'employer': 'slate' },
{ 'name': 'fred', 'blocked': false, 'employer': 'slate' },
{ 'name': 'pebbles', 'blocked': true, 'employer': 'na' }
];
// using "_.pluck" callback shorthand
_.first(characters, 'blocked');
// => [{ 'name': 'barney', 'blocked': true, 'employer': 'slate' }]
// using "_.where" callback shorthand
_.pluck(_.first(characters, { 'employer': 'slate' }), 'name');
// => ['barney', 'fred']
_.flatten(array, [isShallow=false], [callback=identity], [thisArg])
Flattens a nested array (the nesting can be to any depth). If isShallow
is truey, the array will only be flattened a single level. If a callback
is provided each element of the array is passed through the callback before
flattening. The callback is bound to thisArg and invoked with three
arguments; (value, index, array).
If a property name is provided for callback the created ".pluck" style
callback will return the property value of the given element.
If an object is provided for callback the created ".where" style callback
will return true for elements that have the properties of the given object,
else false.
Arguments
array(Array): The array to flatten.[isShallow=false](boolean): A flag to restrict flattening to a single level.[callback=identity](Function|Object|string): The function called per iteration. If a property name or object is provided it will be used to create a ".pluck" or ".where" style callback, respectively.[thisArg](*): Thethisbinding ofcallback.
Returns
(Array): Returns a new flattened array.
Example
_.flatten([1, [2], [3, [[4]]]]);
// => [1, 2, 3, 4];
_.flatten([1, [2], [3, [[4]]]], true);
// => [1, 2, 3, [[4]]];
var characters = [
{ 'name': 'barney', 'age': 30, 'pets': ['hoppy'] },
{ 'name': 'fred', 'age': 40, 'pets': ['baby puss', 'dino'] }
];
// using "_.pluck" callback shorthand
_.flatten(characters, 'pets');
// => ['hoppy', 'baby puss', 'dino']
_.indexOf(array, value, [fromIndex=0])
Gets the index at which the first occurrence of value is found using
strict equality for comparisons, i.e. ===. If the array is already sorted
providing true for fromIndex will run a faster binary search.
Arguments
array(Array): The array to search.value(*): The value to search for.[fromIndex=0](boolean|number): The index to search from ortrueto perform a binary search on a sorted array.
Returns
(number): Returns the index of the matched value or -1.
Example
_.indexOf([1, 2, 3, 1, 2, 3], 2);
// => 1
_.indexOf([1, 2, 3, 1, 2, 3], 2, 3);
// => 4
_.indexOf([1, 1, 2, 2, 3, 3], 2, true);
// => 2
_.initial(array, [callback=1], [thisArg])
Gets all but the last element or last n elements of an array. If a
callback is provided elements at the end of the array are excluded from
the result as long as the callback returns truey. The callback is bound
to thisArg and invoked with three arguments; (value, index, array).
If a property name is provided for callback the created ".pluck" style
callback will return the property value of the given element.
If an object is provided for callback the created ".where" style callback
will return true for elements that have the properties of the given object,
else false.
Arguments
array(Array): The array to query.[callback=1](Function|Object|number|string): The function called per element or the number of elements to exclude. If a property name or object is provided it will be used to create a ".pluck" or ".where" style callback, respectively.[thisArg](*): Thethisbinding ofcallback.
Returns
(Array): Returns a slice of array.
Example
_.initial([1, 2, 3]);
// => [1, 2]
_.initial([1, 2, 3], 2);
// => [1]
_.initial([1, 2, 3], function(num) {
return num > 1;
});
// => [1]
var characters = [
{ 'name': 'barney', 'blocked': false, 'employer': 'slate' },
{ 'name': 'fred', 'blocked': true, 'employer': 'slate' },
{ 'name': 'pebbles', 'blocked': true, 'employer': 'na' }
];
// using "_.pluck" callback shorthand
_.initial(characters, 'blocked');
// => [{ 'name': 'barney', 'blocked': false, 'employer': 'slate' }]
// using "_.where" callback shorthand
_.pluck(_.initial(characters, { 'employer': 'na' }), 'name');
// => ['barney', 'fred']
_.intersection([array])
Creates an array of unique values present in all provided arrays using
strict equality for comparisons, i.e. ===.
Arguments
[array](...Array): The arrays to inspect.
Returns
(Array): Returns an array of shared values.
Example
_.intersection([1, 2, 3], [5, 2, 1, 4], [2, 1]);
// => [1, 2]
_.last(array, [callback], [thisArg])
Gets the last element or last n elements of an array. If a callback is
provided elements at the end of the array are returned as long as the
callback returns truey. The callback is bound to thisArg and invoked
with three arguments; (value, index, array).
If a property name is provided for callback the created ".pluck" style
callback will return the property value of the given element.
If an object is provided for callback the created ".where" style callback
will return true for elements that have the properties of the given object,
else false.
Arguments
array(Array): The array to query.[callback](Function|Object|number|string): The function called per element or the number of elements to return. If a property name or object is provided it will be used to create a ".pluck" or ".where" style callback, respectively.[thisArg](*): Thethisbinding ofcallback.
Returns
(*): Returns the last element(s) of array.
Example
_.last([1, 2, 3]);
// => 3
_.last([1, 2, 3], 2);
// => [2, 3]
_.last([1, 2, 3], function(num) {
return num > 1;
});
// => [2, 3]
var characters = [
{ 'name': 'barney', 'blocked': false, 'employer': 'slate' },
{ 'name': 'fred', 'blocked': true, 'employer': 'slate' },
{ 'name': 'pebbles', 'blocked': true, 'employer': 'na' }
];
// using "_.pluck" callback shorthand
_.pluck(_.last(characters, 'blocked'), 'name');
// => ['fred', 'pebbles']
// using "_.where" callback shorthand
_.last(characters, { 'employer': 'na' });
// => [{ 'name': 'pebbles', 'blocked': true, 'employer': 'na' }]
_.lastIndexOf(array, value, [fromIndex=array.length-1])
Gets the index at which the last occurrence of value is found using strict
equality for comparisons, i.e. ===. If fromIndex is negative, it is used
as the offset from the end of the collection.
If a property name is provided for callback the created ".pluck" style
callback will return the property value of the given element.
If an object is provided for callback the created ".where" style callback
will return true for elements that have the properties of the given object,
else false.
Arguments
array(Array): The array to search.value(*): The value to search for.[fromIndex=array.length-1](number): The index to search from.
Returns
(number): Returns the index of the matched value or -1.
Example
_.lastIndexOf([1, 2, 3, 1, 2, 3], 2);
// => 4
_.lastIndexOf([1, 2, 3, 1, 2, 3], 2, 3);
// => 1
_.pull(array, [value])
Removes all provided values from the given array using strict equality for
comparisons, i.e. ===.
Arguments
array(Array): The array to modify.[value](...*): The values to remove.
Returns
(Array): Returns array.
Example
var array = [1, 2, 3, 1, 2, 3];
_.pull(array, 2, 3);
console.log(array);
// => [1, 1]
_.range([start=0], end, [step=1])
Creates an array of numbers (positive and/or negative) progressing from
start up to but not including end. If start is less than stop a
zero-length range is created unless a negative step is specified.
Arguments
[start=0](number): The start of the range.end(number): The end of the range.[step=1](number): The value to increment or decrement by.
Returns
(Array): Returns a new range array.
Example
_.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);
// => []
_.remove(array, [callback=identity], [thisArg])
Removes all elements from an array that the callback returns truey for
and returns an array of removed elements. The callback is bound to thisArg
and invoked with three arguments; (value, index, array).
If a property name is provided for callback the created ".pluck" style
callback will return the property value of the given element.
If an object is provided for callback the created ".where" style callback
will return true for elements that have the properties of the given object,
else false.
Arguments
array(Array): The array to modify.[callback=identity](Function|Object|string): The function called per iteration. If a property name or object is provided it will be used to create a ".pluck" or ".where" style callback, respectively.[thisArg](*): Thethisbinding ofcallback.
Returns
(Array): Returns a new array of removed elements.
Example
var array = [1, 2, 3, 4, 5, 6];
var evens = _.remove(array, function(num) { return num % 2 == 0; });
console.log(array);
// => [1, 3, 5]
console.log(evens);
// => [2, 4, 6]
_.rest(array, [callback=1], [thisArg])
The opposite of _.initial this method gets all but the first element or
first n elements of an array. If a callback function is provided elements
at the beginning of the array are excluded from the result as long as the
callback returns truey. The callback is bound to thisArg and invoked
with three arguments; (value, index, array).
If a property name is provided for callback the created ".pluck" style
callback will return the property value of the given element.
If an object is provided for callback the created ".where" style callback
will return true for elements that have the properties of the given object,
else false.
Aliases
_.drop, _.tail
Arguments
array(Array): The array to query.[callback=1](Function|Object|number|string): The function called per element or the number of elements to exclude. If a property name or object is provided it will be used to create a ".pluck" or ".where" style callback, respectively.[thisArg](*): Thethisbinding ofcallback.
Returns
(Array): Returns a slice of array.
Example
_.rest([1, 2, 3]);
// => [2, 3]
_.rest([1, 2, 3], 2);
// => [3]
_.rest([1, 2, 3], function(num) {
return num < 3;
});
// => [3]
var characters = [
{ 'name': 'barney', 'blocked': true, 'employer': 'slate' },
{ 'name': 'fred', 'blocked': false, 'employer': 'slate' },
{ 'name': 'pebbles', 'blocked': true, 'employer': 'na' }
];
// using "_.pluck" callback shorthand
_.pluck(_.rest(characters, 'blocked'), 'name');
// => ['fred', 'pebbles']
// using "_.where" callback shorthand
_.rest(characters, { 'employer': 'slate' });
// => [{ 'name': 'pebbles', 'blocked': true, 'employer': 'na' }]
_.sortedIndex(array, value, [callback=identity], [thisArg])
Uses a binary search to determine the smallest index at which a value
should be inserted into a given sorted array in order to maintain the sort
order of the array. If a callback is provided it will be executed for
value and each element of array to compute their sort ranking. The
callback is bound to thisArg and invoked with one argument; (value).
If a property name is provided for callback the created ".pluck" style
callback will return the property value of the given element.
If an object is provided for callback the created ".where" style callback
will return true for elements that have the properties of the given object,
else false.
Arguments
array(Array): The array to inspect.value(*): The value to evaluate.[callback=identity](Function|Object|string): The function called per iteration. If a property name or object is provided it will be used to create a ".pluck" or ".where" style callback, respectively.[thisArg](*): Thethisbinding ofcallback.
Returns
(number): Returns the index at which value should be inserted
into array.
Example
_.sortedIndex([20, 30, 50], 40);
// => 2
// using "_.pluck" callback shorthand
_.sortedIndex([{ 'x': 20 }, { 'x': 30 }, { 'x': 50 }], { 'x': 40 }, 'x');
// => 2
var dict = {
'wordToNumber': { 'twenty': 20, 'thirty': 30, 'fourty': 40, 'fifty': 50 }
};
_.sortedIndex(['twenty', 'thirty', 'fifty'], 'fourty', function(word) {
return dict.wordToNumber[word];
});
// => 2
_.sortedIndex(['twenty', 'thirty', 'fifty'], 'fourty', function(word) {
return this.wordToNumber[word];
}, dict);
// => 2
_.union([array])
Creates an array of unique values, in order, of the provided arrays using
strict equality for comparisons, i.e. ===.
Arguments
[array](...Array): The arrays to inspect.
Returns
(Array): Returns an array of combined values.
Example
_.union([1, 2, 3], [5, 2, 1, 4], [2, 1]);
// => [1, 2, 3, 5, 4]
_.uniq(array, [isSorted=false], [callback=identity], [thisArg])
Creates a duplicate-value-free version of an array using strict equality
for comparisons, i.e. ===. If the array is sorted, providing
true for isSorted will use a faster algorithm. If a callback is provided
each element of array is passed through the callback before uniqueness
is computed. The callback is bound to thisArg and invoked with three
arguments; (value, index, array).
If a property name is provided for callback the created ".pluck" style
callback will return the property value of the given element.
If an object is provided for callback the created ".where" style callback
will return true for elements that have the properties of the given object,
else false.
Aliases
_.unique
Arguments
array(Array): The array to process.[isSorted=false](boolean): A flag to indicate thatarrayis sorted.[callback=identity](Function|Object|string): The function called per iteration. If a property name or object is provided it will be used to create a ".pluck" or ".where" style callback, respectively.[thisArg](*): Thethisbinding ofcallback.
Returns
(Array): Returns a duplicate-value-free array.
Example
_.uniq([1, 2, 1, 3, 1]);
// => [1, 2, 3]
_.uniq([1, 1, 2, 2, 3], true);
// => [1, 2, 3]
_.uniq(['A', 'b', 'C', 'a', 'B', 'c'], function(letter) { return letter.toLowerCase(); });
// => ['A', 'b', 'C']
_.uniq([1, 2.5, 3, 1.5, 2, 3.5], function(num) { return this.floor(num); }, Math);
// => [1, 2.5, 3]
// using "_.pluck" callback shorthand
_.uniq([{ 'x': 1 }, { 'x': 2 }, { 'x': 1 }], 'x');
// => [{ 'x': 1 }, { 'x': 2 }]
_.without(array, [value])
Creates an array excluding all provided values using strict equality for
comparisons, i.e. ===.
Arguments
array(Array): The array to filter.[value](...*): The values to exclude.
Returns
(Array): Returns a new array of filtered values.
Example
_.without([1, 2, 1, 0, 3, 1, 4], 0, 1);
// => [2, 3, 4]
_.xor([array])
Creates an array that is the symmetric difference of the provided arrays. See http://en.wikipedia.org/wiki/Symmetric_difference.
Arguments
[array](...Array): The arrays to inspect.
Returns
(Array): Returns an array of values.
Example
_.xor([1, 2, 3], [5, 2, 1, 4]);
// => [3, 5, 4]
_.xor([1, 2, 5], [2, 3, 5], [3, 4, 5]);
// => [1, 4, 5]
_.zip([array])
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.
Aliases
_.unzip
Arguments
[array](...Array): Arrays to process.
Returns
(Array): Returns a new array of grouped elements.
Example
_.zip(['fred', 'barney'], [30, 40], [true, false]);
// => [['fred', 30, true], ['barney', 40, false]]
_.zipObject(keys, [values=[]])
Creates an object composed from arrays of keys and values. Provide
either a single two dimensional array, i.e. [[key1, value1], [key2, value2]]
or two arrays, one of keys and one of corresponding values.
Aliases
_.object
Arguments
keys(Array): The array of keys.[values=[]](Array): The array of values.
Returns
(Object): Returns an object composed of the given keys and corresponding values.
Example
_.zipObject(['fred', 'barney'], [30, 40]);
// => { 'fred': 30, 'barney': 40 }
“Chaining” Methods
_(value)
Creates a lodash object which wraps the given value to enable intuitive
method chaining.
In addition to Lo-Dash methods, wrappers also have the following Array methods:
concat, join, pop, push, reverse, shift, slice, sort, splice,
and unshift
Chaining is supported in custom builds as long as the value method is
implicitly or explicitly included in the build.
The chainable wrapper functions are:
after, assign, bind, bindAll, bindKey, chain, compact,
compose, concat, countBy, create, createCallback, curry,
debounce, defaults, defer, delay, difference, filter, flatten,
forEach, forEachRight, forIn, forInRight, forOwn, forOwnRight,
functions, groupBy, indexBy, initial, intersection, invert,
invoke, keys, map, max, memoize, merge, min, object, omit,
once, pairs, partial, partialRight, pick, pluck, pull, push,
range, reject, remove, rest, reverse, shuffle, slice, sort,
sortBy, splice, tap, throttle, times, toArray, transform,
union, uniq, unshift, unzip, values, where, without, wrap,
and zip
The non-chainable wrapper functions are:
clone, cloneDeep, contains, escape, every, find, findIndex,
findKey, findLast, findLastIndex, findLastKey, has, identity,
indexOf, isArguments, isArray, isBoolean, isDate, isElement,
isEmpty, isEqual, isFinite, isFunction, isNaN, isNull, isNumber,
isObject, isPlainObject, isRegExp, isString, isUndefined, join,
lastIndexOf, mixin, noConflict, parseInt, pop, random, reduce,
reduceRight, result, shift, size, some, sortedIndex, runInContext,
template, unescape, uniqueId, and value
The wrapper functions first and last return wrapped values when n is
provided, otherwise they return unwrapped values.
Explicit chaining can be enabled by using the _.chain method.
Arguments
value(*): The value to wrap in alodashinstance.
Returns
(Object): Returns a lodash instance.
Example
var wrapped = _([1, 2, 3]);
// returns an unwrapped value
wrapped.reduce(function(sum, num) {
return sum + num;
});
// => 6
// returns a wrapped value
var squares = wrapped.map(function(num) {
return num * num;
});
_.isArray(squares);
// => false
_.isArray(squares.value());
// => true
_.chain(value)
Creates a lodash object that wraps the given value with explicit
method chaining enabled.
Arguments
value(*): The value to wrap.
Returns
(Object): Returns the wrapper object.
Example
var characters = [
{ 'name': 'barney', 'age': 36 },
{ 'name': 'fred', 'age': 40 },
{ 'name': 'pebbles', 'age': 1 }
];
var youngest = _.chain(characters)
.sortBy('age')
.map(function(chr) { return chr.name + ' is ' + chr.age; })
.first()
.value();
// => 'pebbles is 1'
_.tap(value, interceptor)
Invokes interceptor with the value as the first argument and then
returns value. The purpose of this method is to "tap into" a method
chain in order to perform operations on intermediate results within
the chain.
Arguments
value(*): The value to provide tointerceptor.interceptor(Function): The function to invoke.
Returns
(*): Returns value.
Example
_([1, 2, 3, 4])
.tap(function(array) { array.pop(); })
.reverse()
.value();
// => [3, 2, 1]
_.prototype.chain()
Enables explicit method chaining on the wrapper object.
Returns
(*): Returns the wrapper object.
Example
var characters = [
{ 'name': 'barney', 'age': 36 },
{ 'name': 'fred', 'age': 40 }
];
// without explicit chaining
_(characters).first();
// => { 'name': 'barney', 'age': 36 }
// with explicit chaining
_(characters).chain()
.first()
.pick('age')
.value();
// => { 'age': 36 }
_.prototype.toString()
Produces the toString result of the wrapped value.
Returns
(string): Returns the string result.
Example
_([1, 2, 3]).toString();
// => '1,2,3'
_.prototype.valueOf()
Extracts the wrapped value.
Aliases
_.prototype.value
Returns
(*): Returns the wrapped value.
Example
_([1, 2, 3]).valueOf();
// => [1, 2, 3]
“Collections” Methods
_.at(collection, [index])
Creates an array of elements from the specified indexes, or keys, of the
collection. Indexes may be specified as individual arguments or as arrays
of indexes.
Arguments
collection(Array|Object|string): The collection to iterate over.[index](...(number|number[]|string|string[]): The indexes ofcollectionto retrieve, specified as individual indexes or arrays of indexes.
Returns
(Array): Returns a new array of elements corresponding to the provided indexes.
Example
_.at(['a', 'b', 'c', 'd', 'e'], [0, 2, 4]);
// => ['a', 'c', 'e']
_.at(['fred', 'barney', 'pebbles'], 0, 2);
// => ['fred', 'pebbles']
_.contains(collection, target, [fromIndex=0])
Checks if a given value is present in a collection using strict equality
for comparisons, i.e. ===. If fromIndex is negative, it is used as the
offset from the end of the collection.
Aliases
_.include
Arguments
collection(Array|Object|string): The collection to iterate over.target(*): The value to check for.[fromIndex=0](number): The index to search from.
Returns
(boolean): Returns true if the target element is found, else false.
Example
_.contains([1, 2, 3], 1);
// => true
_.contains([1, 2, 3], 1, 2);
// => false
_.contains({ 'name': 'fred', 'age': 40 }, 'fred');
// => true
_.contains('pebbles', 'eb');
// => true
_.countBy(collection, [callback=identity], [thisArg])
Creates an object composed of keys generated from the results of running
each element of collection through the callback. The corresponding value
of each key is the number of times the key was returned by the callback.
The callback is bound to thisArg and invoked with three arguments;
(value, index|key, collection).
If a property name is provided for callback the created ".pluck" style
callback will return the property value of the given element.
If an object is provided for callback the created ".where" style callback
will return true for elements that have the properties of the given object,
else false.
Arguments
collection(Array|Object|string): The collection to iterate over.[callback=identity](Function|Object|string): The function called per iteration. If a property name or object is provided it will be used to create a ".pluck" or ".where" style callback, respectively.[thisArg](*): Thethisbinding ofcallback.
Returns
(Object): Returns the composed aggregate object.
Example
_.countBy([4.3, 6.1, 6.4], function(num) { return Math.floor(num); });
// => { '4': 1, '6': 2 }
_.countBy([4.3, 6.1, 6.4], function(num) { return this.floor(num); }, Math);
// => { '4': 1, '6': 2 }
_.countBy(['one', 'two', 'three'], 'length');
// => { '3': 2, '5': 1 }
_.every(collection, [callback=identity], [thisArg])
Checks if the given callback returns truey value for all elements of
a collection. The callback is bound to thisArg and invoked with three
arguments; (value, index|key, collection).
If a property name is provided for callback the created ".pluck" style
callback will return the property value of the given element.
If an object is provided for callback the created ".where" style callback
will return true for elements that have the properties of the given object,
else false.
Aliases
_.all
Arguments
collection(Array|Object|string): The collection to iterate over.[callback=identity](Function|Object|string): The function called per iteration. If a property name or object is provided it will be used to create a ".pluck" or ".where" style callback, respectively.[thisArg](*): Thethisbinding ofcallback.
Returns
(boolean): Returns true if all elements passed the callback check,
else false.
Example
_.every([true, 1, null, 'yes']);
// => false
var characters = [
{ 'name': 'barney', 'age': 36 },
{ 'name': 'fred', 'age': 40 }
];
// using "_.pluck" callback shorthand
_.every(characters, 'age');
// => true
// using "_.where" callback shorthand
_.every(characters, { 'age': 36 });
// => false
_.filter(collection, [callback=identity], [thisArg])
Iterates over elements of a collection, returning an array of all elements
the callback returns truey for. The callback is bound to thisArg and
invoked with three arguments; (value, index|key, collection).
If a property name is provided for callback the created ".pluck" style
callback will return the property value of the given element.
If an object is provided for callback the created ".where" style callback
will return true for elements that have the properties of the given object,
else false.
Aliases
_.select
Arguments
collection(Array|Object|string): The collection to iterate over.[callback=identity](Function|Object|string): The function called per iteration. If a property name or object is provided it will be used to create a ".pluck" or ".where" style callback, respectively.[thisArg](*): Thethisbinding ofcallback.
Returns
(Array): Returns a new array of elements that passed the callback check.
Example
var evens = _.filter([1, 2, 3, 4, 5, 6], function(num) { return num % 2 == 0; });
// => [2, 4, 6]
var characters = [
{ 'name': 'barney', 'age': 36, 'blocked': false },
{ 'name': 'fred', 'age': 40, 'blocked': true }
];
// using "_.pluck" callback shorthand
_.filter(characters, 'blocked');
// => [{ 'name': 'fred', 'age': 40, 'blocked': true }]
// using "_.where" callback shorthand
_.filter(characters, { 'age': 36 });
// => [{ 'name': 'barney', 'age': 36, 'blocked': false }]
_.find(collection, [callback=identity], [thisArg])
Iterates over elements of a collection, returning the first element that
the callback returns truey for. The callback is bound to thisArg and
invoked with three arguments; (value, index|key, collection).
If a property name is provided for callback the created ".pluck" style
callback will return the property value of the given element.
If an object is provided for callback the created ".where" style callback
will return true for elements that have the properties of the given object,
else false.
Aliases
_.detect, _.findWhere
Arguments
collection(Array|Object|string): The collection to iterate over.[callback=identity](Function|Object|string): The function called per iteration. If a property name or object is provided it will be used to create a ".pluck" or ".where" style callback, respectively.[thisArg](*): Thethisbinding ofcallback.
Returns
(*): Returns the found element, else undefined.
Example
var characters = [
{ 'name': 'barney', 'age': 36, 'blocked': false },
{ 'name': 'fred', 'age': 40, 'blocked': true },
{ 'name': 'pebbles', 'age': 1, 'blocked': false }
];
_.find(characters, function(chr) {
return chr.age < 40;
});
// => { 'name': 'barney', 'age': 36, 'blocked': false }
// using "_.where" callback shorthand
_.find(characters, { 'age': 1 });
// => { 'name': 'pebbles', 'age': 1, 'blocked': false }
// using "_.pluck" callback shorthand
_.find(characters, 'blocked');
// => { 'name': 'fred', 'age': 40, 'blocked': true }
_.findLast(collection, [callback=identity], [thisArg])
This method is like _.find except that it iterates over elements
of a collection from right to left.
Arguments
collection(Array|Object|string): The collection to iterate over.[callback=identity](Function|Object|string): The function called per iteration. If a property name or object is provided it will be used to create a ".pluck" or ".where" style callback, respectively.[thisArg](*): Thethisbinding ofcallback.
Returns
(*): Returns the found element, else undefined.
Example
_.findLast([1, 2, 3, 4], function(num) {
return num % 2 == 1;
});
// => 3
_.forEach(collection, [callback=identity], [thisArg])
Iterates over elements of a collection, executing the callback for each
element. The callback is bound to thisArg and invoked with three arguments;
(value, index|key, collection). Callbacks 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 _.forIn or _.forOwn
may be used for object iteration.
Aliases
_.each
Arguments
collection(Array|Object|string): The collection to iterate over.[callback=identity](Function): The function called per iteration.[thisArg](*): Thethisbinding ofcallback.
Returns
(Array|Object|string): Returns collection.
Example
_([1, 2, 3]).forEach(function(num) { console.log(num); }).join(',');
// => logs each number and returns '1,2,3'
_.forEach({ 'one': 1, 'two': 2, 'three': 3 }, function(num) { console.log(num); });
// => logs each number and returns the object (property order is not guaranteed across environments)
_.forEachRight(collection, [callback=identity], [thisArg])
This method is like _.forEach except that it iterates over elements
of a collection from right to left.
Aliases
_.eachRight
Arguments
collection(Array|Object|string): The collection to iterate over.[callback=identity](Function): The function called per iteration.[thisArg](*): Thethisbinding ofcallback.
Returns
(Array|Object|string): Returns collection.
Example
_([1, 2, 3]).forEachRight(function(num) { console.log(num); }).join(',');
// => logs each number from right to left and returns '3,2,1'
_.groupBy(collection, [callback=identity], [thisArg])
Creates an object composed of keys generated from the results of running
each element of a collection through the callback. The corresponding value
of each key is an array of the elements responsible for generating the key.
The callback is bound to thisArg and invoked with three arguments;
(value, index|key, collection).
If a property name is provided for callback the created ".pluck" style
callback will return the property value of the given element.
If an object is provided for callback the created ".where" style callback
will return true for elements that have the properties of the given object,
else false
Arguments
collection(Array|Object|string): The collection to iterate over.[callback=identity](Function|Object|string): The function called per iteration. If a property name or object is provided it will be used to create a ".pluck" or ".where" style callback, respectively.[thisArg](*): Thethisbinding ofcallback.
Returns
(Object): Returns the composed aggregate object.
Example
_.groupBy([4.2, 6.1, 6.4], function(num) { return Math.floor(num); });
// => { '4': [4.2], '6': [6.1, 6.4] }
_.groupBy([4.2, 6.1, 6.4], function(num) { return this.floor(num); }, Math);
// => { '4': [4.2], '6': [6.1, 6.4] }
// using "_.pluck" callback shorthand
_.groupBy(['one', 'two', 'three'], 'length');
// => { '3': ['one', 'two'], '5': ['three'] }
_.indexBy(collection, [callback=identity], [thisArg])
Creates an object composed of keys generated from the results of running
each element of the collection through the given callback. The corresponding
value of each key is the last element responsible for generating the key.
The callback is bound to thisArg and invoked with three arguments;
(value, index|key, collection).
If a property name is provided for callback the created ".pluck" style
callback will return the property value of the given element.
If an object is provided for callback the created ".where" style callback
will return true for elements that have the properties of the given object,
else false.
Arguments
collection(Array|Object|string): The collection to iterate over.[callback=identity](Function|Object|string): The function called per iteration. If a property name or object is provided it will be used to create a ".pluck" or ".where" style callback, respectively.[thisArg](*): Thethisbinding ofcallback.
Returns
(Object): Returns the composed aggregate object.
Example
var keys = [
{ 'dir': 'left', 'code': 97 },
{ 'dir': 'right', 'code': 100 }
];
_.indexBy(keys, 'dir');
// => { 'left': { 'dir': 'left', 'code': 97 }, 'right': { 'dir': 'right', 'code': 100 } }
_.indexBy(keys, function(key) { return String.fromCharCode(key.code); });
// => { 'a': { 'dir': 'left', 'code': 97 }, 'd': { 'dir': 'right', 'code': 100 } }
_.indexBy(characters, function(key) { this.fromCharCode(key.code); }, String);
// => { 'a': { 'dir': 'left', 'code': 97 }, 'd': { 'dir': 'right', 'code': 100 } }
_.invoke(collection, methodName, [arg])
Invokes the method named by methodName on each element in the collection
returning an array of the results of each invoked method. Additional arguments
will be provided to each invoked method. If methodName is a function it
will be invoked for, and this bound to, each element in the collection.
Arguments
collection(Array|Object|string): The collection to iterate over.methodName(Function|string): The name of the method to invoke or the function invoked per iteration.[arg](...*): Arguments to invoke the method with.
Returns
(Array): Returns a new array of the results of each invoked method.
Example
_.invoke([[5, 1, 7], [3, 2, 1]], 'sort');
// => [[1, 5, 7], [1, 2, 3]]
_.invoke([123, 456], String.prototype.split, '');
// => [['1', '2', '3'], ['4', '5', '6']]
_.map(collection, [callback=identity], [thisArg])
Creates an array of values by running each element in the collection
through the callback. The callback is bound to thisArg and invoked with
three arguments; (value, index|key, collection).
If a property name is provided for callback the created ".pluck" style
callback will return the property value of the given element.
If an object is provided for callback the created ".where" style callback
will return true for elements that have the properties of the given object,
else false.
Aliases
_.collect
Arguments
collection(Array|Object|string): The collection to iterate over.[callback=identity](Function|Object|string): The function called per iteration. If a property name or object is provided it will be used to create a ".pluck" or ".where" style callback, respectively.[thisArg](*): Thethisbinding ofcallback.
Returns
(Array): Returns a new array of the results of each callback execution.
Example
_.map([1, 2, 3], function(num) { return num * 3; });
// => [3, 6, 9]
_.map({ 'one': 1, 'two': 2, 'three': 3 }, function(num) { return num * 3; });
// => [3, 6, 9] (property order is not guaranteed across environments)
var characters = [
{ 'name': 'barney', 'age': 36 },
{ 'name': 'fred', 'age': 40 }
];
// using "_.pluck" callback shorthand
_.map(characters, 'name');
// => ['barney', 'fred']
_.max(collection, [callback=identity], [thisArg])
Retrieves the maximum value of a collection. If the collection is empty or
falsey -Infinity is returned. If a callback is provided it will be executed
for each value in the collection to generate the criterion by which the value
is ranked. The callback is bound to thisArg and invoked with three
arguments; (value, index, collection).
If a property name is provided for callback the created ".pluck" style
callback will return the property value of the given element.
If an object is provided for callback the created ".where" style callback
will return true for elements that have the properties of the given object,
else false.
Arguments
collection(Array|Object|string): The collection to iterate over.[callback=identity](Function|Object|string): The function called per iteration. If a property name or object is provided it will be used to create a ".pluck" or ".where" style callback, respectively.[thisArg](*): Thethisbinding ofcallback.
Returns
(*): Returns the maximum value.
Example
_.max([4, 2, 8, 6]);
// => 8
var characters = [
{ 'name': 'barney', 'age': 36 },
{ 'name': 'fred', 'age': 40 }
];
_.max(characters, function(chr) { return chr.age; });
// => { 'name': 'fred', 'age': 40 };
// using "_.pluck" callback shorthand
_.max(characters, 'age');
// => { 'name': 'fred', 'age': 40 };
_.min(collection, [callback=identity], [thisArg])
Retrieves the minimum value of a collection. If the collection is empty or
falsey Infinity is returned. If a callback is provided it will be executed
for each value in the collection to generate the criterion by which the value
is ranked. The callback is bound to thisArg and invoked with three
arguments; (value, index, collection).
If a property name is provided for callback the created ".pluck" style
callback will return the property value of the given element.
If an object is provided for callback the created ".where" style callback
will return true for elements that have the properties of the given object,
else false.
Arguments
collection(Array|Object|string): The collection to iterate over.[callback=identity](Function|Object|string): The function called per iteration. If a property name or object is provided it will be used to create a ".pluck" or ".where" style callback, respectively.[thisArg](*): Thethisbinding ofcallback.
Returns
(*): Returns the minimum value.
Example
_.min([4, 2, 8, 6]);
// => 2
var characters = [
{ 'name': 'barney', 'age': 36 },
{ 'name': 'fred', 'age': 40 }
];
_.min(characters, function(chr) { return chr.age; });
// => { 'name': 'barney', 'age': 36 };
// using "_.pluck" callback shorthand
_.min(characters, 'age');
// => { 'name': 'barney', 'age': 36 };
_.pluck(collection, property)
Retrieves the value of a specified property from all elements in the collection.
Arguments
collection(Array|Object|string): The collection to iterate over.property(string): The name of the property to pluck.
Returns
(Array): Returns a new array of property values.
Example
var characters = [
{ 'name': 'barney', 'age': 36 },
{ 'name': 'fred', 'age': 40 }
];
_.pluck(characters, 'name');
// => ['barney', 'fred']
_.reduce(collection, [callback=identity], [accumulator], [thisArg])
Reduces a collection to a value which is the accumulated result of running
each element in the collection through the callback, where each successive
callback execution consumes the return value of the previous execution. If
accumulator is not provided the first element of the collection will be
used as the initial accumulator value. The callback is bound to thisArg
and invoked with four arguments; (accumulator, value, index|key, collection).
Aliases
_.foldl, _.inject
Arguments
collection(Array|Object|string): The collection to iterate over.[callback=identity](Function): The function called per iteration.[accumulator](*): Initial value of the accumulator.[thisArg](*): Thethisbinding ofcallback.
Returns
(*): Returns the accumulated value.
Example
var sum = _.reduce([1, 2, 3], function(sum, num) {
return sum + num;
});
// => 6
var mapped = _.reduce({ 'a': 1, 'b': 2, 'c': 3 }, function(result, num, key) {
result[key] = num * 3;
return result;
}, {});
// => { 'a': 3, 'b': 6, 'c': 9 }
_.reduceRight(collection, [callback=identity], [accumulator], [thisArg])
This method is like _.reduce except that it iterates over elements
of a collection from right to left.
Aliases
_.foldr
Arguments
collection(Array|Object|string): The collection to iterate over.[callback=identity](Function): The function called per iteration.[accumulator](*): Initial value of the accumulator.[thisArg](*): Thethisbinding ofcallback.
Returns
(*): Returns the accumulated value.
Example
var list = [[0, 1], [2, 3], [4, 5]];
var flat = _.reduceRight(list, function(a, b) { return a.concat(b); }, []);
// => [4, 5, 2, 3, 0, 1]
_.reject(collection, [callback=identity], [thisArg])
The opposite of _.filter this method returns the elements of a
collection that the callback does not return truey for.
If a property name is provided for callback the created ".pluck" style
callback will return the property value of the given element.
If an object is provided for callback the created ".where" style callback
will return true for elements that have the properties of the given object,
else false.
Arguments
collection(Array|Object|string): The collection to iterate over.[callback=identity](Function|Object|string): The function called per iteration. If a property name or object is provided it will be used to create a ".pluck" or ".where" style callback, respectively.[thisArg](*): Thethisbinding ofcallback.
Returns
(Array): Returns a new array of elements that failed the callback check.
Example
var odds = _.reject([1, 2, 3, 4, 5, 6], function(num) { return num % 2 == 0; });
// => [1, 3, 5]
var characters = [
{ 'name': 'barney', 'age': 36, 'blocked': false },
{ 'name': 'fred', 'age': 40, 'blocked': true }
];
// using "_.pluck" callback shorthand
_.reject(characters, 'blocked');
// => [{ 'name': 'barney', 'age': 36, 'blocked': false }]
// using "_.where" callback shorthand
_.reject(characters, { 'age': 36 });
// => [{ 'name': 'fred', 'age': 40, 'blocked': true }]
_.sample(collection, [n])
Retrieves a random element or n random elements from a collection.
Arguments
collection(Array|Object|string): The collection to sample.[n](number): The number of elements to sample.
Returns
(Array): Returns the random sample(s) of collection.
Example
_.sample([1, 2, 3, 4]);
// => 2
_.sample([1, 2, 3, 4], 2);
// => [3, 1]
_.shuffle(collection)
Creates an array of shuffled values, using a version of the Fisher-Yates shuffle. See http://en.wikipedia.org/wiki/Fisher-Yates_shuffle.
Arguments
collection(Array|Object|string): The collection to shuffle.
Returns
(Array): Returns a new shuffled collection.
Example
_.shuffle([1, 2, 3, 4, 5, 6]);
// => [4, 1, 6, 3, 5, 2]
_.size(collection)
Gets the size of the collection by returning collection.length for arrays
and array-like objects or the number of own enumerable properties for objects.
Arguments
collection(Array|Object|string): The collection to inspect.
Returns
(number): Returns collection.length or number of own enumerable properties.
Example
_.size([1, 2]);
// => 2
_.size({ 'one': 1, 'two': 2, 'three': 3 });
// => 3
_.size('pebbles');
// => 7
_.some(collection, [callback=identity], [thisArg])
Checks if the callback returns a truey value for any element of a
collection. The function returns as soon as it finds a passing value and
does not iterate over the entire collection. The callback is bound to
thisArg and invoked with three arguments; (value, index|key, collection).
If a property name is provided for callback the created ".pluck" style
callback will return the property value of the given element.
If an object is provided for callback the created ".where" style callback
will return true for elements that have the properties of the given object,
else false.
Aliases
_.any
Arguments
collection(Array|Object|string): The collection to iterate over.[callback=identity](Function|Object|string): The function called per iteration. If a property name or object is provided it will be used to create a ".pluck" or ".where" style callback, respectively.[thisArg](*): Thethisbinding ofcallback.
Returns
(boolean): Returns true if any element passed the callback check,
else false.
Example
_.some([null, 0, 'yes', false], Boolean);
// => true
var characters = [
{ 'name': 'barney', 'age': 36, 'blocked': false },
{ 'name': 'fred', 'age': 40, 'blocked': true }
];
// using "_.pluck" callback shorthand
_.some(characters, 'blocked');
// => true
// using "_.where" callback shorthand
_.some(characters, { 'age': 1 });
// => false
_.sortBy(collection, [callback=identity], [thisArg])
Creates an array of elements, sorted in ascending order by the results of
running each element in a collection through the callback. This method
performs a stable sort, that is, it will preserve the original sort order
of equal elements. The callback is bound to thisArg and invoked with
three arguments; (value, index|key, collection).
If a property name is provided for callback the created ".pluck" style
callback will return the property value of the given element.
If an array of property names is provided for callback the collection
will be sorted by each property value.
If an object is provided for callback the created ".where" style callback
will return true for elements that have the properties of the given object,
else false.
Arguments
collection(Array|Object|string): The collection to iterate over.[callback=identity](Array|Function|Object|string): The function called per iteration. If a property name or object is provided it will be used to create a ".pluck" or ".where" style callback, respectively.[thisArg](*): Thethisbinding ofcallback.
Returns
(Array): Returns a new array of sorted elements.
Example
_.sortBy([1, 2, 3], function(num) { return Math.sin(num); });
// => [3, 1, 2]
_.sortBy([1, 2, 3], function(num) { return this.sin(num); }, Math);
// => [3, 1, 2]
var characters = [
{ 'name': 'barney', 'age': 36 },
{ 'name': 'fred', 'age': 40 },
{ 'name': 'barney', 'age': 26 },
{ 'name': 'fred', 'age': 30 }
];
// using "_.pluck" callback shorthand
_.map(_.sortBy(characters, 'age'), _.values);
// => [['barney', 26], ['fred', 30], ['barney', 36], ['fred', 40]]
// sorting by multiple properties
_.map(_.sortBy(characters, ['name', 'age']), _.values);
// = > [['barney', 26], ['barney', 36], ['fred', 30], ['fred', 40]]
_.toArray(collection)
Converts the collection to an array.
Arguments
collection(Array|Object|string): The collection to convert.
Returns
(Array): Returns the new converted array.
Example
(function() { return _.toArray(arguments).slice(1); })(1, 2, 3, 4);
// => [2, 3, 4]
_.where(collection, props)
Performs a deep comparison of each element in a collection to the given
properties object, returning an array of all elements that have equivalent
property values.
Arguments
collection(Array|Object|string): The collection to iterate over.props(Object): The object of property values to filter by.
Returns
(Array): Returns a new array of elements that have the given properties.
Example
var characters = [
{ 'name': 'barney', 'age': 36, 'pets': ['hoppy'] },
{ 'name': 'fred', 'age': 40, 'pets': ['baby puss', 'dino'] }
];
_.where(characters, { 'age': 36 });
// => [{ 'name': 'barney', 'age': 36, 'pets': ['hoppy'] }]
_.where(characters, { 'pets': ['dino'] });
// => [{ 'name': 'fred', 'age': 40, 'pets': ['baby puss', 'dino'] }]
“Functions” Methods
_.after(n, func)
Creates a function that executes func, with the this binding and
arguments of the created function, only after being called n times.
Arguments
n(number): The number of times the function must be called beforefuncis executed.func(Function): The function to restrict.
Returns
(Function): Returns the new restricted function.
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 all saves have completed
_.bind(func, [thisArg], [arg])
Creates a function that, when called, invokes func with the this
binding of thisArg and prepends any additional bind arguments to those
provided to the bound function.
Arguments
func(Function): The function to bind.[thisArg](*): Thethisbinding offunc.[arg](...*): Arguments to be partially applied.
Returns
(Function): Returns the new bound function.
Example
var func = function(greeting) {
return greeting + ' ' + this.name;
};
func = _.bind(func, { 'name': 'fred' }, 'hi');
func();
// => 'hi fred'
_.bindAll(object, [methodName])
Binds methods of an object to the object itself, overwriting the existing
method. Method names may be specified as individual arguments or as arrays
of method names. If no method names are provided all the function properties
of object will be bound.
Arguments
object(Object): The object to bind and assign the bound methods to.[methodName](...string): The object method names to bind, specified as individual method names or arrays of method names.
Returns
(Object): Returns object.
Example
var view = {
'label': 'docs',
'onClick': function() { console.log('clicked ' + this.label); }
};
_.bindAll(view);
jQuery('#docs').on('click', view.onClick);
// => logs 'clicked docs', when the button is clicked
_.bindKey(object, key, [arg])
Creates a function that, when called, invokes the method at object[key]
and prepends any additional bindKey arguments to those provided to the bound
function. This method differs from _.bind by allowing bound functions to
reference methods that will be redefined or don't yet exist.
See http://michaux.ca/articles/lazy-function-definition-pattern.
Arguments
object(Object): The object the method belongs to.key(string): The key of the method.[arg](...*): Arguments to be partially applied.
Returns
(Function): Returns the new bound function.
Example
var object = {
'name': 'fred',
'greet': function(greeting) {
return greeting + ' ' + this.name;
}
};
var func = _.bindKey(object, 'greet', 'hi');
func();
// => 'hi fred'
object.greet = function(greeting) {
return greeting + 'ya ' + this.name + '!';
};
func();
// => 'hiya fred!'
_.compose([func])
Creates a function that is the composition of the provided functions,
where each function consumes the return value of the function that follows.
For example, composing the functions f(), g(), and h() produces f(g(h())).
Each function is executed with the this binding of the composed function.
Arguments
[func](...Function): Functions to compose.
Returns
(Function): Returns the new composed function.
Example
var realNameMap = {
'pebbles': 'penelope'
};
var format = function(name) {
name = realNameMap[name.toLowerCase()] || name;
return name.charAt(0).toUpperCase() + name.slice(1).toLowerCase();
};
var greet = function(formatted) {
return 'Hiya ' + formatted + '!';
};
var welcome = _.compose(greet, format);
welcome('pebbles');
// => 'Hiya Penelope!'
_.curry(func, [arity=func.length])
Creates a function which accepts one or more arguments of func that when
invoked either executes func returning its result, if all func arguments
have been provided, or returns a function that accepts one or more of the
remaining func arguments, and so on. The arity of func can be specified
if func.length is not sufficient.
Arguments
func(Function): The function to curry.[arity=func.length](number): The arity offunc.
Returns
(Function): Returns the new curried function.
Example
var curried = _.curry(function(a, b, c) {
console.log(a + b + c);
});
curried(1)(2)(3);
// => 6
curried(1, 2)(3);
// => 6
curried(1, 2, 3);
// => 6
_.debounce(func, wait, [options])
Creates a function that will delay the execution of func until after
wait milliseconds have elapsed since the last time it was invoked.
Provide an options object to indicate that func should be invoked on
the leading and/or trailing edge of the wait timeout. Subsequent calls
to the debounced function will return the result of the last func call.
Note: If leading and trailing options are true func will be called
on the trailing edge of the timeout only if the the debounced function is
invoked more than once during the wait timeout.
Arguments
func(Function): The function to debounce.wait(number): The number of milliseconds to delay.[options](Object): The options object.[options.leading=false](boolean): Specify execution on the leading edge of the timeout.[options.maxWait](number): The maximum timefuncis allowed to be delayed before it's called.[options.trailing=true](boolean): Specify execution on the trailing edge of the timeout.
Returns
(Function): Returns the new debounced function.
Example
// avoid costly calculations while the window size is in flux
var lazyLayout = _.debounce(calculateLayout, 150);
jQuery(window).on('resize', lazyLayout);
// execute `sendMail` when the click event is fired, debouncing subsequent calls
jQuery('#postbox').on('click', _.debounce(sendMail, 300, {
'leading': true,
'trailing': false
});
// ensure `batchLog` is executed once after 1 second of debounced calls
var source = new EventSource('/stream');
source.addEventListener('message', _.debounce(batchLog, 250, {
'maxWait': 1000
}, false);
_.defer(func, [arg])
Defers executing the func function until the current call stack has cleared.
Additional arguments will be provided to func when it is invoked.
Arguments
func(Function): The function to defer.[arg](...*): Arguments to invoke the function with.
Returns
(number): Returns the timer id.
Example
_.defer(function(text) { console.log(text); }, 'deferred');
// logs 'deferred' after one or more milliseconds
_.delay(func, wait, [arg])
Executes the func function after wait milliseconds. Additional arguments
will be provided to func when it is invoked.
Arguments
func(Function): The function to delay.wait(number): The number of milliseconds to delay execution.[arg](...*): Arguments to invoke the function with.
Returns
(number): Returns the timer id.
Example
_.delay(function(text) { console.log(text); }, 1000, 'later');
// => logs 'later' after one second
_.memoize(func, [resolver])
Creates a function that memoizes the result of func. If resolver is
provided it will be used to determine 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 cache key.
The func is executed with the this binding of the memoized function.
The result cache is exposed as the cache property on the memoized function.
Arguments
func(Function): The function to have its output memoized.[resolver](Function): A function used to resolve the cache key.
Returns
(Function): Returns the new memoizing function.
Example
var fibonacci = _.memoize(function(n) {
return n < 2 ? n : fibonacci(n - 1) + fibonacci(n - 2);
});
fibonacci(9)
// => 34
var data = {
'fred': { 'name': 'fred', 'age': 40 },
'pebbles': { 'name': 'pebbles', 'age': 1 }
};
// modifying the result cache
var get = _.memoize(function(name) { return data[name]; }, _.identity);
get('pebbles');
// => { 'name': 'pebbles', 'age': 1 }
get.cache.pebbles.name = 'penelope';
get('pebbles');
// => { 'name': 'penelope', 'age': 1 }
_.once(func)
Creates a function that is restricted to execute func once. Repeat calls to
the function will return the value of the first call. The func is executed
with the this binding of the created function.
Arguments
func(Function): The function to restrict.
Returns
(Function): Returns the new restricted function.
Example
var initialize = _.once(createApplication);
initialize();
initialize();
// `initialize` executes `createApplication` once
_.partial(func, [arg])
Creates a function that, when called, invokes func with any additional
partial arguments prepended to those provided to the new function. This
method is similar to _.bind except it does not alter the this binding.
Arguments
func(Function): The function to partially apply arguments to.[arg](...*): Arguments to be partially applied.
Returns
(Function): Returns the new partially applied function.
Example
var greet = function(greeting, name) { return greeting + ' ' + name; };
var hi = _.partial(greet, 'hi');
hi('fred');
// => 'hi fred'
_.partialRight(func, [arg])
This method is like _.partial except that partial arguments are
appended to those provided to the new function.
Arguments
func(Function): The function to partially apply arguments to.[arg](...*): Arguments to be partially applied.
Returns
(Function): Returns the new partially applied function.
Example
var defaultsDeep = _.partialRight(_.merge, _.defaults);
var options = {
'variable': 'data',
'imports': { 'jq': $ }
};
defaultsDeep(options, _.templateSettings);
options.variable
// => 'data'
options.imports
// => { '_': _, 'jq': $ }
_.throttle(func, wait, [options])
Creates a function that, when executed, will only call the func function
at most once per every wait milliseconds. Provide an options object to
indicate that func should be invoked on the leading and/or trailing edge
of the wait timeout. Subsequent calls to the throttled function will
return the result of the last func call.
Note: If leading and trailing options are true func will be called
on the trailing edge of the timeout only if the the throttled function is
invoked more than once during the wait timeout.
Arguments
func(Function): The function to throttle.wait(number): The number of milliseconds to throttle executions to.[options](Object): The options object.[options.leading=true](boolean): Specify execution on the leading edge of the timeout.[options.trailing=true](boolean): Specify execution on the trailing edge of the timeout.
Returns
(Function): Returns the new throttled function.
Example
// avoid excessively updating the position while scrolling
var throttled = _.throttle(updatePosition, 100);
jQuery(window).on('scroll', throttled);
// execute `renewToken` when the click event is fired, but not more than once every 5 minutes
jQuery('.interactive').on('click', _.throttle(renewToken, 300000, {
'trailing': false
}));
_.wrap(value, wrapper)
Creates a function that provides value to the wrapper function as its
first argument. Additional arguments provided to the function are appended
to those provided to the wrapper function. The wrapper is executed with
the this binding of the created function.
Arguments
value(*): The value to wrap.wrapper(Function): The wrapper function.
Returns
(Function): Returns the new function.
Example
var p = _.wrap(_.escape, function(func, text) {
return '<p>' + func(text) + '</p>';
});
p('Fred, Wilma, & Pebbles');
// => '<p>Fred, Wilma, & Pebbles</p>'
“Objects” Methods
_.assign(object, [source], [callback], [thisArg])
Assigns own enumerable properties of source object(s) to the destination
object. Subsequent sources will overwrite property assignments of previous
sources. If a callback is provided it will be executed to produce the
assigned values. The callback is bound to thisArg and invoked with two
arguments; (objectValue, sourceValue).
Aliases
_.extend
Arguments
object(Object): The destination object.[source](...Object): The source objects.[callback](Function): The function to customize assigning values.[thisArg](*): Thethisbinding ofcallback.
Returns
(Object): Returns the destination object.
Example
_.assign({ 'name': 'fred' }, { 'employer': 'slate' });
// => { 'name': 'fred', 'employer': 'slate' }
var defaults = _.partialRight(_.assign, function(a, b) {
return typeof a == 'undefined' ? b : a;
});
var object = { 'name': 'barney' };
defaults(object, { 'name': 'fred', 'employer': 'slate' });
// => { 'name': 'barney', 'employer': 'slate' }
_.clone(value, [isDeep=false], [callback], [thisArg])
Creates a clone of value. If isDeep is true nested objects will also
be cloned, otherwise they will be assigned by reference. If a callback
is provided it will be executed to produce the cloned values. If the
callback returns undefined cloning will be handled by the method instead.
The callback is bound to thisArg and invoked with one argument; (value).
Arguments
value(*): The value to clone.[isDeep=false](boolean): Specify a deep clone.[callback](Function): The function to customize cloning values.[thisArg](*): Thethisbinding ofcallback.
Returns
(*): Returns the cloned value.
Example
var characters = [
{ 'name': 'barney', 'age': 36 },
{ 'name': 'fred', 'age': 40 }
];
var shallow = _.clone(characters);
shallow[0] === characters[0];
// => true
var deep = _.clone(characters, true);
deep[0] === characters[0];
// => false
_.mixin({
'clone': _.partialRight(_.clone, function(value) {
return _.isElement(value) ? value.cloneNode(false) : undefined;
})
});
var clone = _.clone(document.body);
clone.childNodes.length;
// => 0
_.cloneDeep(value, [callback], [thisArg])
Creates a deep clone of value. If a callback is provided it will be
executed to produce the cloned values. If the callback returns undefined
cloning will be handled by the method instead. The callback is bound to
thisArg and invoked with one argument; (value).
Note: This method is loosely based on the structured clone algorithm. Functions
and DOM nodes are not cloned. The enumerable properties of arguments objects and
objects created by constructors other than Object are cloned to plain Object objects.
See http://www.w3.org/TR/html5/infrastructure.html#internal-structured-cloning-algorithm.
Arguments
value(*): The value to deep clone.[callback](Function): The function to customize cloning values.[thisArg](*): Thethisbinding ofcallback.
Returns
(*): Returns the deep cloned value.
Example
var characters = [
{ 'name': 'barney', 'age': 36 },
{ 'name': 'fred', 'age': 40 }
];
var deep = _.cloneDeep(characters);
deep[0] === characters[0];
// => false
var view = {
'label': 'docs',
'node': element
};
var clone = _.cloneDeep(view, function(value) {
return _.isElement(value) ? value.cloneNode(true) : undefined;
});
clone.node == view.node;
// => false
_.create(prototype, [properties])
Creates an object that inherits from the given prototype object. If a
properties object is provided its own enumerable properties are assigned
to the created object.
Arguments
prototype(Object): The object to inherit from.[properties](Object): The properties to assign to the object.
Returns
(Object): Returns the new object.
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
_.defaults(object, [source])
Assigns own enumerable properties of source object(s) to the destination
object for all destination properties that resolve to undefined. Once a
property is set, additional defaults of the same property will be ignored.
Arguments
object(Object): The destination object.[source](...Object): The source objects.
Returns
(Object): Returns the destination object.
Example
var object = { 'name': 'barney' };
_.defaults(object, { 'name': 'fred', 'employer': 'slate' });
// => { 'name': 'barney', 'employer': 'slate' }
_.findKey(object, [callback=identity], [thisArg])
This method is like _.findIndex except that it returns the key of the
first element that passes the callback check, instead of the element itself.
If a property name is provided for callback the created ".pluck" style
callback will return the property value of the given element.
If an object is provided for callback the created ".where" style callback
will return true for elements that have the properties of the given object,
else false.
Arguments
object(Object): The object to search.[callback=identity](Function|Object|string): The function called per iteration. If a property name or object is provided it will be used to create a ".pluck" or ".where" style callback, respectively.[thisArg](*): Thethisbinding ofcallback.
Returns
(string|undefined): Returns the key of the found element, else undefined.
Example
var characters = {
'barney': { 'age': 36, 'blocked': false },
'fred': { 'age': 40, 'blocked': true },
'pebbles': { 'age': 1, 'blocked': false }
};
_.findKey(characters, function(chr) {
return chr.age < 40;
});
// => 'barney' (property order is not guaranteed across environments)
// using "_.where" callback shorthand
_.findKey(characters, { 'age': 1 });
// => 'pebbles'
// using "_.pluck" callback shorthand
_.findKey(characters, 'blocked');
// => 'fred'
_.findLastKey(object, [callback=identity], [thisArg])
This method is like _.findKey except that it iterates over elements
of a collection in the opposite order.
If a property name is provided for callback the created ".pluck" style
callback will return the property value of the given element.
If an object is provided for callback the created ".where" style callback
will return true for elements that have the properties of the given object,
else false.
Arguments
object(Object): The object to search.[callback=identity](Function|Object|string): The function called per iteration. If a property name or object is provided it will be used to create a ".pluck" or ".where" style callback, respectively.[thisArg](*): Thethisbinding ofcallback.
Returns
(string|undefined): Returns the key of the found element, else undefined.
Example
var characters = {
'barney': { 'age': 36, 'blocked': true },
'fred': { 'age': 40, 'blocked': false },
'pebbles': { 'age': 1, 'blocked': true }
};
_.findLastKey(characters, function(chr) {
return chr.age < 40;
});
// => returns `pebbles`, assuming `_.findKey` returns `barney`
// using "_.where" callback shorthand
_.findLastKey(characters, { 'age': 40 });
// => 'fred'
// using "_.pluck" callback shorthand
_.findLastKey(characters, 'blocked');
// => 'pebbles'
_.forIn(object, [callback=identity], [thisArg])
Iterates over own and inherited enumerable properties of an object,
executing the callback for each property. The callback is bound to thisArg
and invoked with three arguments; (value, key, object). Callbacks may exit
iteration early by explicitly returning false.
Arguments
object(Object): The object to iterate over.[callback=identity](Function): The function called per iteration.[thisArg](*): Thethisbinding ofcallback.
Returns
(Object): Returns object.
Example
function Shape() {
this.x = 0;
this.y = 0;
}
Shape.prototype.move = function(x, y) {
this.x += x;
this.y += y;
};
_.forIn(new Shape, function(value, key) {
console.log(key);
});
// => logs 'x', 'y', and 'move' (property order is not guaranteed across environments)
_.forInRight(object, [callback=identity], [thisArg])
This method is like _.forIn except that it iterates over elements
of a collection in the opposite order.
Arguments
object(Object): The object to iterate over.[callback=identity](Function): The function called per iteration.[thisArg](*): Thethisbinding ofcallback.
Returns
(Object): Returns object.
Example
function Shape() {
this.x = 0;
this.y = 0;
}
Shape.prototype.move = function(x, y) {
this.x += x;
this.y += y;
};
_.forInRight(new Shape, function(value, key) {
console.log(key);
});
// => logs 'move', 'y', and 'x' assuming `_.forIn ` logs 'x', 'y', and 'move'
_.forOwn(object, [callback=identity], [thisArg])
Iterates over own enumerable properties of an object, executing the callback
for each property. The callback is bound to thisArg and invoked with three
arguments; (value, key, object). Callbacks may exit iteration early by
explicitly returning false.
Arguments
object(Object): The object to iterate over.[callback=identity](Function): The function called per iteration.[thisArg](*): Thethisbinding ofcallback.
Returns
(Object): Returns object.
Example
_.forOwn({ '0': 'zero', '1': 'one', 'length': 2 }, function(num, key) {
console.log(key);
});
// => logs '0', '1', and 'length' (property order is not guaranteed across environments)
_.forOwnRight(object, [callback=identity], [thisArg])
This method is like _.forOwn except that it iterates over elements
of a collection in the opposite order.
Arguments
object(Object): The object to iterate over.[callback=identity](Function): The function called per iteration.[thisArg](*): Thethisbinding ofcallback.
Returns
(Object): Returns object.
Example
_.forOwnRight({ '0': 'zero', '1': 'one', 'length': 2 }, function(num, key) {
console.log(key);
});
// => logs 'length', '1', and '0' assuming `_.forOwn` logs '0', '1', and 'length'
_.functions(object)
Creates a sorted array of property names of all enumerable properties,
own and inherited, of object that have function values.
Aliases
_.methods
Arguments
object(Object): The object to inspect.
Returns
(Array): Returns an array of property names that have function values.
Example
_.functions(_);
// => ['all', 'any', 'bind', 'bindAll', 'clone', 'compact', 'compose', ...]
_.has(object, key)
Checks if the specified property name exists as a direct property of object,
instead of an inherited property.
Arguments
object(Object): The object to inspect.key(string): The name of the property to check.
Returns
(boolean): Returns true if key is a direct property, else false.
Example
_.has({ 'a': 1, 'b': 2, 'c': 3 }, 'b');
// => true
_.invert(object)
Creates an object composed of the inverted keys and values of the given object.
Arguments
object(Object): The object to invert.
Returns
(Object): Returns the created inverted object.
Example
_.invert({ 'first': 'fred', 'second': 'barney' });
// => { 'fred': 'first', 'barney': 'second' }
_.isArguments(value)
Checks if value is an arguments object.
Arguments
value(*): The value to check.
Returns
(boolean): Returns true if the value is an arguments object, else false.
Example
(function() { return _.isArguments(arguments); })(1, 2, 3);
// => true
_.isArguments([1, 2, 3]);
// => false
_.isArray(value)
Checks if value is an array.
Arguments
value(*): The value to check.
Returns
(boolean): Returns true if the value is an array, else false.
Example
(function() { return _.isArray(arguments); })();
// => false
_.isArray([1, 2, 3]);
// => true
_.isBoolean(value)
Checks if value is a boolean value.
Arguments
value(*): The value to check.
Returns
(boolean): Returns true if the value is a boolean value, else false.
Example
_.isBoolean(null);
// => false
_.isDate(value)
Checks if value is a date.
Arguments
value(*): The value to check.
Returns
(boolean): Returns true if the value is a date, else false.
Example
_.isDate(new Date);
// => true
_.isElement(value)
Checks if value is a DOM element.
Arguments
value(*): The value to check.
Returns
(boolean): Returns true if the value is a DOM element, else false.
Example
_.isElement(document.body);
// => true
_.isEmpty(value)
Checks if value is empty. Arrays, strings, or arguments objects with a
length of 0 and objects with no own enumerable properties are considered
"empty".
Arguments
value(Array|Object|string): The value to inspect.
Returns
(boolean): Returns true if the value is empty, else false.
Example
_.isEmpty([1, 2, 3]);
// => false
_.isEmpty({});
// => true
_.isEmpty('');
// => true
_.isEqual(a, b, [callback], [thisArg])
Performs a deep comparison between two values to determine if they are
equivalent to each other. If a callback is provided it will be executed
to compare values. If the callback returns undefined comparisons will
be handled by the method instead. The callback is bound to thisArg and
invoked with two arguments; (a, b).
Arguments
a(*): The value to compare.b(*): The other value to compare.[callback](Function): The function to customize comparing values.[thisArg](*): Thethisbinding ofcallback.
Returns
(boolean): Returns true if the values are equivalent, else false.
Example
var object = { 'name': 'fred' };
var copy = { 'name': 'fred' };
object == copy;
// => false
_.isEqual(object, copy);
// => true
var words = ['hello', 'goodbye'];
var otherWords = ['hi', 'goodbye'];
_.isEqual(words, otherWords, function(a, b) {
var reGreet = /^(?:hello|hi)$/i,
aGreet = _.isString(a) && reGreet.test(a),
bGreet = _.isString(b) && reGreet.test(b);
return (aGreet || bGreet) ? (aGreet == bGreet) : undefined;
});
// => true
_.isFinite(value)
Checks if value is, or can be coerced to, a finite number.
Note: This is not the same as native isFinite which will return true for
booleans and empty strings. See http://es5.github.io/#x15.1.2.5.
Arguments
value(*): The value to check.
Returns
(boolean): Returns true if the value is finite, else false.
Example
_.isFinite(-101);
// => true
_.isFinite('10');
// => true
_.isFinite(true);
// => false
_.isFinite('');
// => false
_.isFinite(Infinity);
// => false
_.isFunction(value)
Checks if value is a function.
Arguments
value(*): The value to check.
Returns
(boolean): Returns true if the value is a function, else false.
Example
_.isFunction(_);
// => true
_.isNaN(value)
Checks if value is NaN.
Note: This is not the same as native isNaN which will return true for
undefined and other non-numeric values. See http://es5.github.io/#x15.1.2.4.
Arguments
value(*): The value to check.
Returns
(boolean): Returns true if the value is NaN, else false.
Example
_.isNaN(NaN);
// => true
_.isNaN(new Number(NaN));
// => true
isNaN(undefined);
// => true
_.isNaN(undefined);
// => false
_.isNull(value)
Checks if value is null.
Arguments
value(*): The value to check.
Returns
(boolean): Returns true if the value is null, else false.
Example
_.isNull(null);
// => true
_.isNull(undefined);
// => false
_.isNumber(value)
Checks if value is a number.
Note: NaN is considered a number. See http://es5.github.io/#x8.5.
Arguments
value(*): The value to check.
Returns
(boolean): Returns true if the value is a number, else false.
Example
_.isNumber(8.4 * 5);
// => true
_.isObject(value)
Checks if value is the language type of Object.
(e.g. arrays, functions, objects, regexes, new Number(0), and new String(''))
Arguments
value(*): The value to check.
Returns
(boolean): Returns true if the value is an object, else false.
Example
_.isObject({});
// => true
_.isObject([1, 2, 3]);
// => true
_.isObject(1);
// => false
_.isPlainObject(value)
Checks if value is an object created by the Object constructor.
Arguments
value(*): The value to check.
Returns
(boolean): Returns true if value is a plain object, else false.
Example
function Shape() {
this.x = 0;
this.y = 0;
}
_.isPlainObject(new Shape);
// => false
_.isPlainObject([1, 2, 3]);
// => false
_.isPlainObject({ 'x': 0, 'y': 0 });
// => true
_.isRegExp(value)
Checks if value is a regular expression.
Arguments
value(*): The value to check.
Returns
(boolean): Returns true if the value is a regular expression, else false.
Example
_.isRegExp(/fred/);
// => true
_.isString(value)
Checks if value is a string.
Arguments
value(*): The value to check.
Returns
(boolean): Returns true if the value is a string, else false.
Example
_.isString('fred');
// => true
_.isUndefined(value)
Checks if value is undefined.
Arguments
value(*): The value to check.
Returns
(boolean): Returns true if the value is undefined, else false.
Example
_.isUndefined(void 0);
// => true
_.keys(object)
Creates an array composed of the own enumerable property names of an object.
Arguments
object(Object): The object to inspect.
Returns
(Array): Returns an array of property names.
Example
_.keys({ 'one': 1, 'two': 2, 'three': 3 });
// => ['one', 'two', 'three'] (property order is not guaranteed across environments)
_.mapValues(object, [callback=identity], [thisArg])
Creates an object with the same keys as object and values generated by
running each own enumerable property of object through the callback.
The callback is bound to thisArg and invoked with three arguments;
(value, key, object).
If a property name is provided for callback the created ".pluck" style
callback will return the property value of the given element.
If an object is provided for callback the created ".where" style callback
will return true for elements that have the properties of the given object,
else false.
Arguments
object(Object): The object to iterate over.[callback=identity](Function|Object|string): The function called per iteration. If a property name or object is provided it will be used to create a ".pluck" or ".where" style callback, respectively.[thisArg](*): Thethisbinding ofcallback.
Returns
(Array): Returns a new object with values of the results of each callback execution.
Example
_.mapValues({ 'a': 1, 'b': 2, 'c': 3} , function(num) { return num * 3; });
// => { 'a': 3, 'b': 6, 'c': 9 }
var characters = {
'fred': { 'name': 'fred', 'age': 40 },
'pebbles': { 'name': 'pebbles', 'age': 1 }
};
// using "_.pluck" callback shorthand
_.mapValues(characters, 'age');
// => { 'fred': 40, 'pebbles': 1 }
_.merge(object, [source], [callback], [thisArg])
Recursively merges own enumerable properties of the source object(s), that
don't resolve to undefined into the destination object. Subsequent sources
will overwrite property assignments of previous sources. If a callback is
provided it will be executed to produce the merged values of the destination
and source properties. If the callback returns undefined merging will
be handled by the method instead. The callback is bound to thisArg and
invoked with two arguments; (objectValue, sourceValue).
Arguments
object(Object): The destination object.[source](...Object): The source objects.[callback](Function): The function to customize merging properties.[thisArg](*): Thethisbinding ofcallback.
Returns
(Object): Returns the destination object.
Example
var names = {
'characters': [
{ 'name': 'barney' },
{ 'name': 'fred' }
]
};
var ages = {
'characters': [
{ 'age': 36 },
{ 'age': 40 }
]
};
_.merge(names, ages);
// => { 'characters': [{ 'name': 'barney', 'age': 36 }, { 'name': 'fred', 'age': 40 }] }
var food = {
'fruits': ['apple'],
'vegetables': ['beet']
};
var otherFood = {
'fruits': ['banana'],
'vegetables': ['carrot']
};
_.merge(food, otherFood, function(a, b) {
return _.isArray(a) ? a.concat(b) : undefined;
});
// => { 'fruits': ['apple', 'banana'], 'vegetables': ['beet', 'carrot] }
_.omit(object, [callback], [thisArg])
Creates a shallow clone of object excluding the specified properties.
Property names may be specified as individual arguments or as arrays of
property names. If a callback is provided it will be executed for each
property of object omitting the properties the callback returns truey
for. The callback is bound to thisArg and invoked with three arguments;
(value, key, object).
Arguments
object(Object): The source object.[callback](Function|...string|string[]): The properties to omit or the function called per iteration.[thisArg](*): Thethisbinding ofcallback.
Returns
(Object): Returns an object without the omitted properties.
Example
_.omit({ 'name': 'fred', 'age': 40 }, 'age');
// => { 'name': 'fred' }
_.omit({ 'name': 'fred', 'age': 40 }, function(value) {
return typeof value == 'number';
});
// => { 'name': 'fred' }
_.pairs(object)
Creates a two dimensional array of an object's key-value pairs,
i.e. [[key1, value1], [key2, value2]].
Arguments
object(Object): The object to inspect.
Returns
(Array): Returns new array of key-value pairs.
Example
_.pairs({ 'barney': 36, 'fred': 40 });
// => [['barney', 36], ['fred', 40]] (property order is not guaranteed across environments)
_.pick(object, [callback], [thisArg])
Creates a shallow clone of object composed of the specified properties.
Property names may be specified as individual arguments or as arrays of
property names. If a callback is provided it will be executed for each
property of object picking the properties the callback returns truey
for. The callback is bound to thisArg and invoked with three arguments;
(value, key, object).
Arguments
object(Object): The source object.[callback](Function|...string|string[]): The function called per iteration or property names to pick, specified as individual property names or arrays of property names.[thisArg](*): Thethisbinding ofcallback.
Returns
(Object): Returns an object composed of the picked properties.
Example
_.pick({ 'name': 'fred', '_userid': 'fred1' }, 'name');
// => { 'name': 'fred' }
_.pick({ 'name': 'fred', '_userid': 'fred1' }, function(value, key) {
return key.charAt(0) != '_';
});
// => { 'name': 'fred' }
_.transform(object, [callback=identity], [accumulator], [thisArg])
An alternative to _.reduce this method transforms object to a new
accumulator object which is the result of running each of its own
enumerable properties through a callback, with each callback execution
potentially mutating the accumulator object. The callback is bound to
thisArg and invoked with four arguments; (accumulator, value, key, object).
Callbacks may exit iteration early by explicitly returning false.
Arguments
object(Array|Object): The object to iterate over.[callback=identity](Function): The function called per iteration.[accumulator](*): The custom accumulator value.[thisArg](*): Thethisbinding ofcallback.
Returns
(*): Returns the accumulated value.
Example
var squares = _.transform([1, 2, 3, 4, 5, 6, 7, 8, 9, 10], function(result, num) {
num *= num;
if (num % 2) {
return result.push(num) < 3;
}
});
// => [1, 9, 25]
var mapped = _.transform({ 'a': 1, 'b': 2, 'c': 3 }, function(result, num, key) {
result[key] = num * 3;
});
// => { 'a': 3, 'b': 6, 'c': 9 }
_.values(object)
Creates an array composed of the own enumerable property values of object.
Arguments
object(Object): The object to inspect.
Returns
(Array): Returns an array of property values.
Example
_.values({ 'one': 1, 'two': 2, 'three': 3 });
// => [1, 2, 3] (property order is not guaranteed across environments)
“Utilities” Methods
_.constant(value)
Creates a function that returns value.
Arguments
value(*): The value to return from the new function.
Returns
(Function): Returns the new function.
Example
var object = { 'name': 'fred' };
var getter = _.constant(object);
getter() === object;
// => true
_.createCallback([func=identity], [thisArg], [argCount])
Produces a callback bound to an optional thisArg. If func is a property
name the created callback will return the property value for a given element.
If func is an object the created callback will return true for elements
that contain the equivalent object properties, otherwise it will return false.
Arguments
[func=identity](*): The value to convert to a callback.[thisArg](*): Thethisbinding of the created callback.[argCount](number): The number of arguments the callback accepts.
Returns
(Function): Returns a callback function.
Example
var characters = [
{ 'name': 'barney', 'age': 36 },
{ 'name': 'fred', 'age': 40 }
];
// wrap to create custom callback shorthands
_.createCallback = _.wrap(_.createCallback, function(func, callback, thisArg) {
var match = /^(.+?)__([gl]t)(.+)$/.exec(callback);
return !match ? func(callback, thisArg) : function(object) {
return match[2] == 'gt' ? object[match[1]] > match[3] : object[match[1]] < match[3];
};
});
_.filter(characters, 'age__gt38');
// => [{ 'name': 'fred', 'age': 40 }]
_.escape(string)
Converts the characters &, <, >, ", and ' in string to their
corresponding HTML entities.
Arguments
string(string): The string to escape.
Returns
(string): Returns the escaped string.
Example
_.escape('Fred, Wilma, & Pebbles');
// => 'Fred, Wilma, & Pebbles'
_.identity(value)
This method returns the first argument provided to it.
Arguments
value(*): Any value.
Returns
(*): Returns value.
Example
var object = { 'name': 'fred' };
_.identity(object) === object;
// => true
_.mixin([object=lodash], source, [options])
Adds function properties of a source object to the destination object.
If object is a function methods will be added to its prototype as well.
Arguments
[object=lodash](Function|Object): object The destination object.source(Object): The object of functions to add.[options](Object): The options object.[options.chain=true](boolean): Specify whether the functions added are chainable.
Example
function capitalize(string) {
return string.charAt(0).toUpperCase() + string.slice(1).toLowerCase();
}
_.mixin({ 'capitalize': capitalize });
_.capitalize('fred');
// => 'Fred'
_('fred').capitalize().value();
// => 'Fred'
_.mixin({ 'capitalize': capitalize }, { 'chain': false });
_('fred').capitalize();
// => 'Fred'
_.noConflict()
Reverts the '_' variable to its previous value and returns a reference to
the lodash function.
Returns
(Function): Returns the lodash function.
Example
var lodash = _.noConflict();
_.noop()
A no-operation function.
Example
var object = { 'name': 'fred' };
_.noop(object) === undefined;
// => true
_.now
Gets the number of milliseconds that have elapsed since the Unix epoch (1 January 1970 00:00:00 UTC).
Example
var stamp = _.now();
_.defer(function() { console.log(_.now() - stamp); });
// => logs the number of milliseconds it took for the deferred function to be called
_.parseInt(value, [radix])
Converts the given value into an integer of the specified radix.
If radix is undefined or 0 a radix of 10 is used unless the
value is a hexadecimal, in which case a radix of 16 is used.
Note: This method avoids differences in native ES3 and ES5 parseInt
implementations. See http://es5.github.io/#E.
Arguments
value(string): The value to parse.[radix](number): The radix used to interpret the value to parse.
Returns
(number): Returns the new integer value.
Example
_.parseInt('08');
// => 8
_.property(key)
Creates a "_.pluck" style function, which returns the key value of a
given object.
Arguments
key(string): The name of the property to retrieve.
Returns
(Function): Returns the new function.
Example
var characters = [
{ 'name': 'fred', 'age': 40 },
{ 'name': 'barney', 'age': 36 }
];
var getName = _.property('name');
_.map(characters, getName);
// => ['barney', 'fred']
_.sortBy(characters, getName);
// => [{ 'name': 'barney', 'age': 36 }, { 'name': 'fred', 'age': 40 }]
_.random([min=0], [max=1], [floating=false])
Produces a random number between min and max (inclusive). If only one
argument is provided a number between 0 and the given number will be
returned. If floating is truey or either min or max are floats a
floating-point number will be returned instead of an integer.
Arguments
[min=0](number): The minimum possible value.[max=1](number): The maximum possible value.[floating=false](boolean): Specify returning a floating-point number.
Returns
(number): Returns a random number.
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
_.result(object, key)
Resolves the value of property key on object. If key is a function
it will be invoked with the this binding of object and its result returned,
else the property value is returned. If object is falsey then undefined
is returned.
Arguments
object(Object): The object to inspect.key(string): The name of the property to resolve.
Returns
(*): Returns the resolved value.
Example
var object = {
'cheese': 'crumpets',
'stuff': function() {
return 'nonsense';
}
};
_.result(object, 'cheese');
// => 'crumpets'
_.result(object, 'stuff');
// => 'nonsense'
_.runInContext([context=root])
Create a new lodash function using the given context object.
Arguments
[context=root](Object): The context object.
Returns
(Function): Returns the lodash function.
_.template(text, data, [options], [sourceURL], [variable])
A micro-templating method that handles arbitrary delimiters, preserves
whitespace, and correctly escapes quotes within interpolated code.
Note: In the development build, _.template utilizes sourceURLs for easier
debugging. See http://www.html5rocks.com/en/tutorials/developertools/sourcemaps/#toc-sourceurl
For more information on precompiling templates see:
https://lodash.com/custom-builds
For more information on Chrome extension sandboxes see:
http://developer.chrome.com/stable/extensions/sandboxingEval.html
Arguments
text(string): The template text.data(Object): The data object used to populate the text.[options](Object): The options object.[options.escape](RegExp): The "escape" delimiter.[options.evaluate](RegExp): The "evaluate" delimiter.[options.imports](Object): An object to import into the template as local variables.[options.interpolate](RegExp): The "interpolate" delimiter.[sourceURL](string): The sourceURL of the template's compiled source.[variable](string): The data object variable name.
Returns
(Function|string): Returns a compiled function when no data object
is given, else it returns the interpolated text.
Example
// using the "interpolate" delimiter to create a compiled template
var compiled = _.template('hello <%= name %>');
compiled({ 'name': 'fred' });
// => 'hello fred'
// using the "escape" delimiter to escape HTML in data property values
_.template('<b><%- value %></b>', { 'value': '<script>' });
// => '<b><script></b>'
// using the "evaluate" delimiter to generate HTML
var list = '<% _.forEach(people, function(name) { %><li><%- name %></li><% }); %>';
_.template(list, { 'people': ['fred', 'barney'] });
// => '<li>fred</li><li>barney</li>'
// using the ES6 delimiter as an alternative to the default "interpolate" delimiter
_.template('hello ${ name }', { 'name': 'pebbles' });
// => 'hello pebbles'
// using the internal `print` function in "evaluate" delimiters
_.template('<% print("hello " + name); %>!', { 'name': 'barney' });
// => 'hello barney!'
// using a custom template delimiters
_.templateSettings = {
'interpolate': /{{([\s\S]+?)}}/g
};
_.template('hello {{ name }}!', { 'name': 'mustache' });
// => 'hello mustache!'
// using the `imports` option to import jQuery
var list = '<% jq.each(people, function(name) { %><li><%- name %></li><% }); %>';
_.template(list, { 'people': ['fred', 'barney'] }, { 'imports': { 'jq': jQuery } });
// => '<li>fred</li><li>barney</li>'
// using the `sourceURL` option to specify a custom sourceURL for the template
var compiled = _.template('hello <%= name %>', null, { 'sourceURL': '/basic/greeting.jst' });
compiled(data);
// => find the source of "greeting.jst" under the Sources tab or Resources panel of the web inspector
// using the `variable` option to ensure a with-statement isn't used in the compiled template
var compiled = _.template('hi <%= data.name %>!', null, { 'variable': 'data' });
compiled.source;
// => function(data) {
var __t, __p = '', __e = _.escape;
__p += 'hi ' + ((__t = ( data.name )) == null ? '' : __t) + '!';
return __p;
}
// using the `source` property to inline compiled templates for meaningful
// line numbers in error messages and a stack trace
fs.writeFileSync(path.join(cwd, 'jst.js'), '\
var JST = {\
"main": ' + _.template(mainText).source + '\
};\
');
_.times(n, callback, [thisArg])
Executes the callback n times, returning an array of the results
of each callback execution. The callback is bound to thisArg and invoked
with one argument; (index).
Arguments
n(number): The number of times to execute the callback.callback(Function): The function called per iteration.[thisArg](*): Thethisbinding ofcallback.
Returns
(Array): Returns an array of the results of each callback execution.
Example
var diceRolls = _.times(3, _.partial(_.random, 1, 6));
// => [3, 6, 4]
_.times(3, function(n) { mage.castSpell(n); });
// => calls `mage.castSpell(n)` three times, passing `n` of `0`, `1`, and `2` respectively
_.times(3, function(n) { this.cast(n); }, mage);
// => also calls `mage.castSpell(n)` three times
_.unescape(string)
The inverse of _.escape this method converts the HTML entities
&, <, >, ", and ' in string to their
corresponding characters.
Arguments
string(string): The string to unescape.
Returns
(string): Returns the unescaped string.
Example
_.unescape('Fred, Barney & Pebbles');
// => 'Fred, Barney & Pebbles'
_.uniqueId([prefix])
Generates a unique ID. If prefix is provided the ID will be appended to it.
Arguments
[prefix](string): The value to prefix the ID with.
Returns
(string): Returns the unique ID.
Example
_.uniqueId('contact_');
// => 'contact_104'
_.uniqueId();
// => '105'
Methods
_.templateSettings.imports._
A reference to the lodash function.
Properties
_.VERSION
(string): The semantic version number.
_.support
(Object): An object used to flag environments features.
_.support.argsClass
(boolean): Detect if an arguments object's Class is resolvable (all but Firefox < 4, IE < 9).
_.support.argsObject
(boolean): Detect if arguments objects are Object objects (all but Narwhal and Opera < 10.5).
_.support.enumErrorProps
(boolean): Detect if name or message properties of Error.prototype are
enumerable by default. (IE < 9, Safari < 5.1)
_.support.enumPrototypes
(boolean): Detect if prototype properties are enumerable by default.
Firefox < 3.6, Opera > 9.50 - Opera < 11.60, and Safari < 5.1
(if the prototype or a property on the prototype has been set)
incorrectly sets a function's prototype property Enumerable
value to true.
_.support.funcDecomp
(boolean): Detect if functions can be decompiled by Function#toString
(all but PS3 and older Opera mobile browsers & avoided in Windows 8 apps).
_.support.funcNames
(boolean): Detect if Function#name is supported (all but IE).
_.support.nonEnumArgs
(boolean): Detect if arguments object indexes are non-enumerable
(Firefox < 4, IE < 9, PhantomJS, Safari < 5.1).
_.support.nonEnumShadows
(boolean): Detect if properties shadowing those on Object.prototype are non-enumerable.
In IE < 9 an objects own properties, shadowing non-enumerable ones, are
made non-enumerable as well (a.k.a the JScript DontEnum bug).
_.support.ownLast
(boolean): Detect if own properties are iterated after inherited properties (all but IE < 9).
_.support.spliceObjects
(boolean): Detect if Array#shift and Array#splice augment array-like objects correctly.
Firefox < 10, IE compatibility mode, and IE < 9 have buggy Array shift()
and splice() functions that fail to remove the last element, value[0],
of array-like objects even though the length property is set to 0.
The shift() method is buggy in IE 8 compatibility mode, while splice()
is buggy regardless of mode in IE < 9 and buggy in compatibility mode in IE 9.
_.support.unindexedChars
(boolean): Detect lack of support for accessing string characters by index.
IE < 8 can't access characters by index and IE 8 can only access
characters by index on string literals.
_.templateSettings
(Object): By default, the template delimiters used by Lo-Dash are similar to those in embedded Ruby (ERB). Change the following template settings to use alternative delimiters.
_.templateSettings.escape
(RegExp): Used to detect data property values to be HTML-escaped.
_.templateSettings.evaluate
(RegExp): Used to detect code to be evaluated.
_.templateSettings.imports
(Object): Used to import variables into the compiled template.
_.templateSettings.interpolate
(RegExp): Used to detect data property values to inject.
_.templateSettings.variable
(string): Used to reference the data object in the template text.