A drop-in replacement for Underscore.js that delivers performance improvements, bug fixes, and additional features.
JavaScript Other
Pull request Compare This branch is 291 commits ahead, 7181 commits behind lodash:master.
Fetching latest commit…
Cannot retrieve the latest commit at this time.
Failed to load latest commit information.


Lo-Dash v0.3.2

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.

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

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


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



Lo-Dash has been tested in at least Chrome 5-19, Firefox 1.5-13, IE 6-9, Opera 9.25-12, 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.

  • Backbone builds, containing all methods required by Backbone, may be created using the backbone modifier argument.
node build backbone
  • Mobile builds, with IE bug fixes and method compilation removed, may be created using the mobile modifier argument.
node build mobile

Custom builds may be created in three ways:

  1. Use the category argument to pass the categories of methods to include in the build.
    Valid categories are "arrays", "chaining", "collections", "functions", "objects", and "utilities".
node build category=collections,functions
node build category="collections, functions"
  1. Use the include argument to pass the names of methods to include in the build.
node build include=each,filter,map
node build include="each, filter, map"
  1. Use the exclude argument to pass the names of methods to exclude from the build.
node build exclude=union,uniq,zip
node build exclude="union, uniq, zip"

All arguments, except include and exlcude, may be combined.

node build backbone mobile category=functions include=pick,uniq
node build backbone mobile category=utilities exclude=first,last

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

Installation and usage

In browsers:

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

or use the CDN:
<script src="http://cdnjs.cloudflare.com/ajax/libs/lodash.js/0.3.2/lodash.min.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:


In an AMD loader like RequireJS:

  'paths': {
    'underscore': 'path/to/lodash'
['underscore'], function(_) {

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

  • Allow iteration of objects with a length property [#148, #154, #252, #448, test]
  • Ensure "Arrays" category methods allow falsey array arguments [test]
  • Ensure array-like objects with invalid length properties are treated like regular objects [test, test, test]
  • Ensure _(…) returns passed wrapper instances [test]
  • Ensure _.escape returns an empty string when passed null or undefined [#407, test]
  • Ensure _.groupBy adds values to own, not inherited, properties [test]
  • Ensure _.sortedIndex supports arrays with high length values [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
  • _.times
  • _.toArray
  • _.union
  • _.uniq, _.unique
  • _.values
  • _.without
  • _.wrap
  • _.zip
  • plus all _(…) method wrappers

Release Notes


  • Deprecated _(…).chain, _.isFinite, _.isNaN, _.isNull, _.isUndefined, _.result, and _.size
  • Ensured _.escape returns an empty string when passed null or undefined
  • Ensured sourceURL support doesn't cause errors in Adobe's JS engine.
  • Fixed regression in generating custom builds
  • Moved _.invoke and _.pluck back to the "Collections" category
  • Moved _.tap to the "Chaining" category

The full changelog is available here.


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.