_.attempt(func)

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

Arguments

1. func (Function): The function to attempt.

Returns

(*): Returns the func result or error object.

Example

// avoid throwing errors for invalid selectors
var elements = _.attempt(function(selector) {
  return document.querySelectorAll(selector);
}, '>_>');
if (_.isError(elements)) {
  elements = [];
}

.callback([func=.identity], [thisArg])

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

Aliases

_.iteratee

Arguments

1. [func=_.identity] (*): The value to convert to a callback.
2. [thisArg] (*): The this binding of func.

Returns

(Function): Returns the callback.

Example

var users = [
  { 'user': 'barney', 'age': 36 },
  { 'user': 'fred',   'age': 40 }
];
// wrap to create custom callback shorthands
_.callback = _.wrap(_.callback, function(callback, func, thisArg) {
  var match = /^(.+?)__([gl]t)(.+)$/.exec(func);
  if (!match) {
    return callback(func, thisArg);
  }
  return function(object) {
    return match[2] == 'gt'
      ? object[match[1]] > match[3]
      : object[match[1]] < match[3];
  };
});
_.filter(users, 'age__gt36');
// => [{ 'user': 'fred', 'age': 40 }]

_.constant(value)

Creates a function that returns value.

Arguments

1. value (*): The value to return from the new function.

Returns

(Function): Returns the new function.

Example

var object = { 'user': 'fred' };
var getter = _.constant(object);
getter() === object;
// => true

_.identity(value)

This method returns the first argument provided to it.

Arguments

1. value (*): Any value.

Returns

(*): Returns value.

Example

var object = { 'user': 'fred' };
_.identity(object) === object;
// => true

_.matches(source)

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

Note: This method supports comparing arrays, booleans, Date objects, numbers, Object objects, regexes, and strings. Objects are compared by their own, not inherited, enumerable properties. For comparing a single own or inherited property value see _.matchesProperty.

Arguments

1. source (Object): The object of property values to match.

Returns

(Function): Returns the new function.

Example

var users = [
  { 'user': 'barney', 'age': 36, 'active': true },
  { 'user': 'fred',   'age': 40, 'active': false }
];
_.filter(users, _.matches({ 'age': 40, 'active': false }));
// => [{ 'user': 'fred', 'age': 40, 'active': false }]

_.matchesProperty(path, srcValue)

Creates a function that compares the property value of path on a given object to value.

Note: This method supports comparing arrays, booleans, Date objects, numbers, Object objects, regexes, and strings. Objects are compared by their own, not inherited, enumerable properties.

Arguments

1. path (Array|string): The path of the property to get.
2. srcValue (*): The value to match.

Returns

(Function): Returns the new function.

Example

var users = [
  { 'user': 'barney' },
  { 'user': 'fred' }
];
_.find(users, _.matchesProperty('user', 'fred'));
// => { 'user': 'fred' }

_.method(path, [args])

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

Arguments

1. path (Array|string): The path of the method to invoke.
2. [args] (…*): The arguments to invoke the method with.

Returns

(Function): Returns the new function.

Example

var objects = [
  { 'a': { 'b': { 'c': _.constant(2) } } },
  { 'a': { 'b': { 'c': _.constant(1) } } }
];
_.map(objects, _.method('a.b.c'));
// => [2, 1]
_.invoke(_.sortBy(objects, _.method(['a', 'b', 'c'])), 'a.b.c');
// => [1, 2]

_.methodOf(object, [args])

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

Arguments

1. object (Object): The object to query.
2. [args] (…*): The arguments to invoke the method with.

Returns

(Function): Returns the new function.

Example

var array = _.times(3, _.constant),
    object = { 'a': array, 'b': array, 'c': array };
_.map(['a[2]', 'c[0]'], _.methodOf(object));
// => [2, 0]
_.map([['a', '2'], ['c', '0']], _.methodOf(object));
// => [2, 0]

_.mixin([object=lodash], source, [options])

Adds all own enumerable function properties of a source object to the destination object. If object is a function then methods are added to its prototype as well.

Note: Use _.runInContext to create a pristine lodash function to avoid conflicts caused by modifying the original.

Arguments

1. [object=lodash] (Function|Object): The destination object.
2. source (Object): The object of functions to add.
3. [options] (Object): The options object.
4. [options.chain=true] (boolean): Specify whether the functions added are chainable.

Returns

(Function|Object): Returns object.

Example

function vowels(string) {
  return _.filter(string, function(v) {
    return /[aeiou]/i.test(v);
  });
}
_.mixin({ 'vowels': vowels });
_.vowels('fred');
// => ['e']
_('fred').vowels().value();
// => ['e']
_.mixin({ 'vowels': vowels }, { 'chain': false });
_('fred').vowels();
// => ['e']

_.noConflict()`

# Ⓢ [Ⓣ][1] Ⓝ

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 that returns undefined regardless of the arguments it receives.

Example

var object = { 'user': 'fred' };
_.noop(object) === undefined;
// => true

_.property(path)

Creates a function that returns the property value at path on a given object.

Arguments

1. path (Array|string): The path of the property to get.

Returns

(Function): Returns the new function.

Example

var objects = [
  { 'a': { 'b': { 'c': 2 } } },
  { 'a': { 'b': { 'c': 1 } } }
];
_.map(objects, _.property('a.b.c'));
// => [2, 1]
_.pluck(_.sortBy(objects, _.property(['a', 'b', 'c'])), 'a.b.c');
// => [1, 2]

_.propertyOf(object)

The opposite of _.property; this method creates a function that returns the property value at a given path on object.

Arguments

1. object (Object): The object to query.

Returns

(Function): Returns the new function.

Example

var array = [0, 1, 2],
    object = { 'a': array, 'b': array, 'c': array };
_.map(['a[2]', 'c[0]'], _.propertyOf(object));
// => [2, 0]
_.map([['a', '2'], ['c', '0']], _.propertyOf(object));
// => [2, 0]

_.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 end is not specified it’s set to start with start then set to 0. If end is less than start a zero-length range is created unless a negative step is specified.

Arguments

1. [start=0] (number): The start of the range.
2. end (number): The end of the range.
3. [step=1] (number): The value to increment or decrement by.

Returns

(Array): Returns the new array of numbers.

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);
// => []

_.runInContext([context=root])

Create a new pristine lodash function using the given context object.

Arguments

1. [context=root] (Object): The context object.

Returns

(Function): Returns a new lodash function.

Example

_.mixin({ 'foo': _.constant('foo') });
var lodash = _.runInContext();
lodash.mixin({ 'bar': lodash.constant('bar') });
_.isFunction(_.foo);
// => true
_.isFunction(_.bar);
// => false
lodash.isFunction(lodash.foo);
// => false
lodash.isFunction(lodash.bar);
// => true
// using `context` to mock `Date#getTime` use in `_.now`
var mock = _.runInContext({
  'Date': function() {
    return { 'getTime': getTimeMock };
  }
});
// or creating a suped-up `defer` in Node.js
var defer = _.runInContext({ 'setTimeout': setImmediate }).defer;

.times(n, [iteratee=.identity], [thisArg])

Invokes the iteratee function n times, returning an array of the results of each invocation. The iteratee is bound to thisArg and invoked with one argument; (index).

Arguments

1. n (number): The number of times to invoke iteratee.
2. [iteratee=_.identity] (Function): The function invoked per iteration.
3. [thisArg] (*): The this binding of iteratee.

Returns

(Array): Returns the array of results.

Example

var diceRolls = _.times(3, _.partial(_.random, 1, 6, false));
// => [3, 6, 4]
_.times(3, function(n) {
  mage.castSpell(n);
});
// => invokes `mage.castSpell(n)` three times with `n` of `0`, `1`, and `2`
_.times(3, function(n) {
  this.cast(n);
}, mage);
// => also invokes `mage.castSpell(n)` three times

_.uniqueId([prefix])

Generates a unique ID. If prefix is provided the ID is appended to it.

Arguments

1. [prefix] (string): The value to prefix the ID with.

Returns

(string): Returns the unique ID.

Example

_.uniqueId('contact_');
// => 'contact_104'
_.uniqueId();
// => '105'