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 ^v0.7.0

A drop-in replacement^* for Underscore.js, from the devs behind jsPerf.com, delivering performance, 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.

Download

• Development source
• Production source
• CDN copies of ≤ v0.7.0 are available on cdnjs thanks to CloudFlare
• For optimal performance, create a custom build with only the features you need

Dive in

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

Create your own benchmarks at jsPerf, or search for existing ones.

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

Screencasts

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

• Introducing Lo-Dash
• Lo-Dash optimizations and custom builds
• Lo-Dash’s origin and why it’s a better utility belt
• Unit testing in Lo-Dash
• Lo-Dash’s approach to native method use

Features

• AMD loader support (RequireJS, curl.js, etc.)
• _.bind supports “lazy” binding
• _.clone supports “deep” cloning
• _.countBy as a companion function for _.groupBy and _.sortBy
• _.debounce’ed functions match _.throttle’ed functions’ return value behavior
• _.forEach is chainable and supports exiting iteration early
• _.forIn for iterating over an object’s own and inherited properties
• _.forOwn for iterating over an object’s own properties
• _.indexOf and _.lastIndexOf accept a fromIndex argument
• _.invert to create inverted objects
• _.merge for a “deep” _.extend
• _.object and _.pairs for composing objects
• _.omit for the inverse functionality of _.pick
• _.partial for partial application without this binding
• _.pick and _.omit accept callback and thisArg arguments
• _.random for generating random numbers within a given range
• _.sortBy performs a stable sort
• _.template utilizes sourceURLs for easier debugging
• _.unescape to unescape strings escaped by _.escape
• _.where for filtering collections by contained properties
• _.countBy, _.groupBy, _.sortedIndex, and _.uniq accept a thisArg argument
• _.contains, _.size, _.toArray, and more… accept strings

Support

Lo-Dash has been tested in at least Chrome 5-21, Firefox 1-15, IE 6-9, Opera 9.25-12, Safari 3-6, Node.js 0.4.8-0.8.8, Narwhal 0.3.2, RingoJS 0.8, and Rhino 1.7RC5.

Custom builds

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

• Backbone builds, with only methods required by Backbone, may be created using the backbone modifier argument.

lodash backbone

• CSP builds, supporting default Content Security Policy restrictions, may be created using the csp modifier argument.

lodash csp

• Legacy builds, tailored for older browsers without ES5 support, may be created using the legacy modifier argument.

lodash legacy

• Mobile builds, with IE < 9 bug fixes and method compilation removed, may be created using the mobile modifier argument.

lodash mobile

• Strict builds, with _.bindAll, _.defaults, and _.extend in strict mode, may be created using the strict modifier argument.

lodash strict

• Underscore builds, with iteration fixes removed and only Underscore’s API, may be created using the underscore modifier argument.

lodash underscore

Custom builds may be created using the following commands:

• Use the category argument to pass comma separated categories of methods to include in the build.
  Valid categories are “arrays”, “chaining”, “collections”, “functions”, “objects”, and “utilities”.

lodash category=collections,functions
lodash category="collections, functions"

• Use the exclude argument to pass comma separated names of methods to exclude from the build.

lodash exclude=union,uniq,zip
lodash exclude="union, uniq, zip"

• Use the exports argument to pass comma separated names of ways to export the LoDash function.
  Valid exports are “amd”, “commonjs”, “global”, “node”, and “none”.

lodash exports=amd,commonjs,node
lodash include="amd, commonjs, node"

• Use the iife argument to specify code to replace the immediately-invoked function expression that wraps Lo-Dash.

lodash iife="!function(window,undefined){%output%}(this)"

• Use the include argument to pass comma separated names of methods to include in the build.

lodash include=each,filter,map
lodash include="each, filter, map"

All arguments, except exclude with include and legacy with csp/mobile, may be combined.

lodash backbone legacy exports=global category=utilities exclude=first,last
lodash -s underscore mobile strict exports=amd category=functions include=pick,uniq

The following options are also supported:

• -c, --stdout Write output to standard output
• -h, --help Display help information
• -o, --output Write output to a given path/filename
• -s, --silent Skip status updates normally logged to the console
• -V, --version Output current version of Lo-Dash

The lodash command-line utility is available when Lo-Dash is installed as a global package (i.e. npm install -g lodash).

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
npm install -g lodash

In Node.js and RingoJS v0.8.0+:

var _ = require('lodash');

In 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);
});

Resolved Underscore.js issues ⁽²⁰⁺⁾

• Allow iteration of objects with a length property [#148, #154, #252, #448, #659, test]
• Ensure array-like objects with invalid length properties are treated like regular objects [#741, test]
• Ensure “Arrays”, “Collections”, and “Objects” methods don’t error when passed falsey arguments [#650, test]
• Ensure “Collections” methods allow string collection arguments [#247, #276, #561, test]
• Fix cross-browser object iteration bugs [#60, #376, test]
• Methods should work on pages with incorrectly shimmed native methods [#7, #742, test]
• Register as an AMD module, but still export to global [#431, test]
• _.clone should allow deep cloning [#595, test]
• _.contains should work with strings [#667, test]
• _.countBy and _.groupBy should only add values to own, not inherited, properties [#736, test]
• _.extend should recursively extend objects [#379, #718, test]
• _.forEach should be chainable [#142, test]
• _.forEach should allow exiting iteration early [#211, test]
• _.isElement should use strict equality for its duck type check [#734, test]
• _.isEmpty should support jQuery/MooTools DOM query collections [#690, test]
• _.isEqual should return true for like-objects from different documents [#733, test]
• _.isEqual should use custom isEqual methods before checking strict equality [#748, test]
• _.isObject should avoid V8 bug #2291 [#605, test]
• _.isNaN(new Number(NaN)) should return true [#749, test]
• _.keys should work with arguments objects cross-browser [#396, test]
• _.range should coerce arguments to numbers [#634, #683, test]
• _.reduceRight should pass correct callback arguments when iterating objects [test]
• _.sortedIndex should support arrays with high length values [#735, test]
• _.throttle should work when called in a loop [#502, test]
• _.toArray uses custom toArray methods of arrays and strings [#747, test]

Optimized methods ⁽⁵⁰⁺⁾

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

Release Notes

^v0.7.0

Compatibility Warnings

• Renamed _.zipObject to _.object
• Replaced _.drop with _.omit
• Made _.drop alias _.rest

Changes

• Added _.invert, _.pairs, and _.random
• Added _.result to the backbone build
• Added exports, iife, -c/--stdout, -o/--output, and -s/--silent build options
• Ensured isPlainObject works with objects from other documements
• Ensured _.isEqual compares values with circular references correctly
• Ensured _.merge work with four or more arguments
• Ensured _.sortBy performs a stable sort for undefined values
• Ensured _.template works with "interpolate" delimiters containing ternary operators
• Ensured the production build works in Node.js
• Ensured template delimiters are tokenized correctly
• Made pseudo private properties _chain and _wrapped double-underscored to avoid conflicts
• Made minify.js support underscore.js
• Reduced the size of mobile and underscore builds
• Simplified _.isEqual and _.size

The full changelog is available here.

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