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.
- Development source
- Production source
- CDN copies of ≤ v0.6.1 are available on cdnjs thanks to CloudFlare
- For optimal performance, create a custom build with only the features you need
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:
- 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
- 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
- _.drop for the inverse functionality of _.pick
- _.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
- _.groupBy, _.sortedIndex, and _.uniq accept a
thisArgargument - _.indexOf and _.lastIndexOf accept a
fromIndexargument - _.merge for a “deep” _.extend
- _.partial for partial application without
thisbinding - _.pick and _.drop accept
callbackandthisArgarguments - _.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
- _.zipObject for composing objects
- _.contains, _.size, _.toArray, and more… accept strings
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 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
backbonemodifier argument.
lodash backbone- CSP builds, supporting default Content Security Policy restrictions, may be created using the
cspmodifier argument.
lodash csp- Legacy builds, tailored for older browsers without ES5 support, may be created using the
legacymodifier argument.
lodash legacy- Mobile builds, with IE < 9 bug fixes and method compilation removed, may be created using the
mobilemodifier argument.
lodash mobile- Strict builds, with
_.bindAll,_.defaults, and_.extendin strict mode, may be created using thestrictmodifier argument.
lodash strict- Underscore builds, containing only methods included in Underscore, may be created using the
underscoremodifier argument.
lodash underscoreCustom builds may be created in three ways:
- Use the
categoryargument to pass the 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
excludeargument to pass the names of methods to exclude from the build.
lodash exclude=union,uniq,zip
lodash exclude="union, uniq, zip"- Use the
includeargument to pass the names of methods to include in the build.
lodash include=each,filter,map
lodash include="each, filter, map"All arguments, except backbone with underscore, exclude with include, and legacy with csp/mobile, may be combined.
lodash backbone legacy category=utilities exclude=first,last
lodash underscore mobile strict category=functions include=pick,uniqThe 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.
In browsers:
<script src="lodash.js"></script>Using npm:
npm install lodash
npm install -g lodashIn 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);
});- Allow iteration of objects with a
lengthproperty [#148, #154, #252, #448, #659, test] - Ensure array-like objects with invalid
lengthproperties are treated like regular objects [test] - Ensure “Arrays”, “Collections”, and “Objects” methods don’t error when passed falsey arguments [#650, test]
- Ensure “Collections” methods allow string
collectionarguments [#247, #276, #561, test] - Ensure templates compiled with errors are inspectable [#666, test]
- Fix cross-browser object iteration bugs [#60, #376, 8000 test]
- Handle arrays with
undefinedvalues correctly in IE < 9 [#601] - Methods should work on pages with incorrectly shimmed native methods [#7, test]
- Register as an AMD module, but still export to global [#431, test]
_(…)should return passed wrapper instances [test]_.cloneshould allowdeepcloning [#595, test]_.containsshould work with strings [#667, test]_.countByand_.groupByshould only add values to own, not inherited, properties [test]_.escapeshould return an empty string when passednullorundefined[#427, test]_.extendshould recursively extend objects [#379, #718, test]_.forEachshould be chainable [#142, test]_.forEachshould allow exiting iteration early [#211, test]_.isElementshould use strict equality for its duck type check [test]_.isEmptyand_.sizeshould support jQuery/MooTools DOM query collections [#690, test]_.isEqualshould returntruefor like-objects from different documents [test]_.isObjectshould avoid V8 bug #2291 [#605, test]_.isNaN(new Number(NaN))should returntrue[test]_.keysand_.sizeshould work withargumentsobjects cross-browser [#396, #653, test]_.onceshould free the given function for garbage collection [#693]_.rangeshould coerce arguments to numbers [#634, #683, test]_.reduceRightshould pass correct callback arguments when iterating objects [test]_.sizeshould return thelengthof string values [test]_.sortedIndexshould support arrays with highlengthvalues [test]_.templateshould not augment theoptionsobject [test]_.throttleshould work when called in a loop [#502, test]_.toArrayuses customtoArraymethods of arrays and strings [test]_.zipObjectshould accept less than two arguments [test]
_.bind_.bindAll_.clone_.compact_.contains,_.include_.defaults_.defer_.difference_.drop,_.omit_.each_.escape_.every,_.all_.extend_.filter,_.select_.find,_.detect_.flatten_.forEach,_.each_.functions,_.methods_.groupBy_.indexOf_.intersection_.invoke_.isArguments_.isDate_.isEmpty_.isFinite_.isFunction_.isObject_.isNumber_.isRegExp_.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
- Ensured IE conditional compilation isn’t enabled by the
useSourceURLtest - Optimized
isPlainObject
- Added
callbackandthisArgarguments to_.dropand_.pick - Added
hasObjectSpliceBugtest to avoiddeleteoperator use - Added
_.omitalias for_.drop - Added _.unescape
- Ensured
_.reduceworks with string objects in IE < 9 - Made compiled methods take advantage of engines with strict mode optimizations
- Optimized
_.intersectionand removed its dependency on_.every - Reduced the file size of the
underscorebuild
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.
