lodash

What is lodash?

Lodash is a JavaScript library that provides utility functions for common programming tasks using a functional programming paradigm. It includes functions for manipulating and traversing arrays, objects, and strings, as well as utilities for functions, language, math, number, object, sequence, and utility methods.

What are lodash's main functionalities?

Array Manipulation

Lodash provides a rich set of array manipulation functions such as map, filter, find, and sort. The code sample demonstrates sorting an array in ascending order using a custom comparator.

[3, 2, 1].sort(_.compareWith(function(a, b) { return a - b; }))

Object Manipulation

Lodash allows for easy manipulation and traversal of objects. The code sample shows how to assign properties from source objects to a destination object.

_.assign({ 'a': 1 }, { 'b': 2 }, { 'c': 3 })

String Manipulation

Lodash includes functions to manipulate strings, such as converting to different cases, trimming, padding, etc. The code sample demonstrates converting a string to kebab-case.

_.kebabCase('Foo Bar')

Function Utilities

Lodash provides function utilities like debounce and throttle to control function invocation. The code sample shows a debounced function that will only be invoked after 250 milliseconds have passed without it being called again.

_.debounce(function() { console.log('Debounced'); }, 250)

Language Utilities

Lodash includes utilities for deep cloning, merging, and comparing objects. The code sample demonstrates deep cloning an object to ensure nested objects are cloned as well.

_.cloneDeep({ 'a': 1, 'b': { 'c': 2 } })

Other packages similar to lodash

underscore

Underscore is a utility library with similar functionality to Lodash, offering a range of functions for manipulating arrays, objects, and functions. It is generally considered to be the predecessor to Lodash, which provides a superset of Underscore's features with additional performance optimizations.

ramda

Ramda is a functional programming library that emphasizes a more functional and composable approach compared to Lodash. It provides similar utilities but focuses on immutability and side-effect free functions, which can lead to a different programming style.

immutable

Immutable.js offers a different take on data manipulation by providing persistent immutable data structures. Unlike Lodash, which works with standard JavaScript objects and arrays, Immutable.js uses its own data structures, which can lead to better performance and easier reasoning about state changes in certain applications.

README

Lo-Dash ^v0.2.2

A drop-in replacement for Underscore.js, from the devs behind jsPerf.com, that delivers performance improvements, bug fixes, and additional features.

Lo-Dash’s performance is gained by avoiding slower native methods, instead opting for simplified non-ES5 compliant methods optimized for common usage, and by leveraging function compilation to reduce the number of overall function calls.

Dive in

We’ve got API docs, benchmarks, and unit tests.

For a list of upcoming features, check out our roadmap.

Screencasts

For more information check out these screencasts over Lo-Dash:

• Introducing Lo-Dash
• Optimizations and custom builds

Features

• AMD loader support
• _.bind supports "lazy" binding
• _.debounce’ed functions match _.throttle’ed functions’ return value behavior
• _.forEach is chainable
• _.groupBy accepts a third, thisArg, argument
• _.partial for more functional fun
• _.size supports returning the length of string values

Support

Lo-Dash has been tested in at least Chrome 5-19, Firefox 1.5-12, IE 6-9, Opera 9.25-11.64, Safari 3.0.4-5.1.3, Node.js 0.4.8-0.6.18, Narwhal 0.3.2, RingoJS 0.8, and Rhino 1.7RC3.

Custom builds

Custom builds make it easy to create lightweight versions of Lo-Dash containing only the methods you need. We handle all the method dependency and alias mapping for you.

Mobile builds, with IE bug fixes and method compilation removed, may be created by using the mobile argument.

node build mobile

Custom builds may be created in two ways:

1. Use theinclude argument to pass the names of the methods to include in the build.

node build include=each,filter,map,noConflict
node build include="each, filter, map, noConflict"
node build mobile include=each,filter,map,noConflict

1. Use the exclude argument to pass the names of the methods to exclude from the build.

node build exclude=isNaN,isUndefined,union,zip
node build exclude="isNaN, isUndefined, union, zip"
node build mobile exclude=isNaN,isUndefined,union,zip

Custom builds are saved to lodash.custom.js and lodash.custom.min.js.

Installation and usage

In browsers:

<script src="lodash.js"></script>

Using npm:

npm install lodash

In Node.js and RingoJS v0.8.0+:

var _ = require('lodash');

In Narwhal and RingoJS v0.7.0-:

var _ = require('lodash')._;

In Rhino:

load('lodash.js');

In an AMD loader like RequireJS:

require({
  'paths': {
    'underscore': 'path/to/lodash'
  }
},
['underscore'], function(_) {
  console.log(_.VERSION);
});

Cloning this repo

To clone this repository including all submodules, using Git 1.6.5 or later:

git clone --recursive https://github.com/bestiejs/lodash.git
cd lodash.js

For older Git versions, just use:

git clone https://github.com/bestiejs/lodash.git
cd lodash
git submodule update --init

Closed Underscore.js issues

• Ensure _(...) returns passed wrapper instances [test]
• Ensure _.groupBy adds values to own, not inherited, properties [test]
• Ensure _.throttle works when called in tight loops [#502, test]
• Fix Firefox, IE, Opera, and Safari object iteration bugs [#376, test, test, test, test, test, test]
• Handle arrays with undefined values correctly in IE < 9 [#601]
• Methods should work on pages with incorrectly shimmed native methods [#7, test]
• Register as AMD module, but still export to global [#431, test]
• _.forEach should be chainable [#142, test]
• _isNaN(new Number(NaN)) should return true [test]
• _.reduceRight should pass correct callback arguments when iterating objects [test]
• _.size should return the length of string values [test]

Optimized methods ⁽⁵⁰⁺⁾

• _.bind
• _.bindAll
• _.clone
• _.compact
• _.contains, _.include
• _.defaults
• _.defer
• _.difference
• _.each
• _.escape
• _.every, _.all
• _.extend
• _.filter, _.select
• _.find, _.detect
• _.flatten
• _.forEach, _.each
• _.functions, _.methods
• _.groupBy
• _.indexOf
• _.intersection
• _.invoke
• _.isEmpty
• _.isEqual
• _.isFinite
• _.isObject
• _.isString
• _.keys
• _.lastIndexOf
• _.map, _.collect
• _.max
• _.memoize
• _.min
• _.mixin
• _.pick
• _.pluck
• _.reduce, _.foldl, _.inject
• _.reject
• _.result
• _.shuffle
• _.some, _.any
• _.sortBy
• _.sortedIndex
• _.template
• _.throttle
• _.toArray
• _.union
• _.uniq, _.unique
• _.values
• _.without
• _.wrap
• _.zip
• plus all _(...) method wrappers

Changelog

^v0.2.2

• Added mobile build option
• Ensured _.find returns undefined for unmatched values
• Ensured _.templateSettings.variable is compatible with Underscore.js
• Optimized _.escape
• Reduced dependencies in _.find

^v0.2.1

• Adjusted the Lo-Dash export order for r.js
• Ensured _.groupBy values are added to own, not inherited, properties
• Made _.bind follow ES5 spec to support a popular Backbone.js pattern
• Removed the alias intersect
• Simplified _.bind, _.flatten, _.groupBy, _.max, and _.min

^v0.2.0

• Added custom build options
• Added default _.templateSettings.variable value
• Added "lazy bind" support to _.bind
• Added native method overwrite detection to avoid bad native shims
• Added support for more AMD build optimizers and aliasing as the "underscore" module
• Added thisArg argument to _.groupBy
• Added whitespace to compiled strings
• Added _.partial method
• Commented the iterationFactory options object
• Ensured _(...) returns passed wrapper instances
• Ensured _.max and _.min support extremely large arrays
• Ensured _.throttle works in tight loops
• Fixed IE < 9 [DontEnum] bug and Firefox < 3.6, Opera > 9.50 - Opera < 11.60, and Safari < 5.1’s prototype property iteration bug
• Inlined _.isFunction calls.
• Made _.debounce’ed functions match _.throttle’ed functions’ return value behavior
• Made _.escape no longer translate the ">" character
• Fixed clearTimeout typo
• Simplified all methods in the "Arrays" category
• Optimized _.debounce, _.escape, _.flatten, _.forEach, _.groupBy, _.intersection, _.invoke, _.isObject, _.max, _.min, _.pick, _.shuffle, _.sortedIndex, _.template, _.throttle, _.union, _.uniq

^v0.1.0

• Initial release

BestieJS

Lo-Dash is part of the BestieJS "Best in Class" module collection. This means we promote solid browser/environment support, ES5 precedents, unit testing, and plenty of documentation.

Author

• John-David Dalton

Contributors

• Kit Cambridge
• Mathias Bynens