Differences between Lodash and Underscore js

Question

Why would someone prefer either the Lodash or Underscore js utility library over the other  Lodash seems to be a drop-in replacement for underscore  the latter having been around longer  I think both are brilliant  but I do not know enough about how they work to make an educated comparison  and I would like to know more about the differences

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In 2014 I still think my point holds  IMHO  this discussion got blown out of proportion quite a bit  Quoting the aforementioned blog post   Most JavaScript utility libraries  such as Underscore  Valentine  and wu  rely on the    native-first dual approach     This approach prefers native implementations  falling back to vanilla JavaScript only if the native equivalent is not supported  But jsPerf revealed an interesting trend  the most efficient way to iterate over an array or array-like collection is to avoid the native implementations entirely  opting for simple loops instead   As if  quot simple loops quot  and  quot vanilla Javascript quot  are more native than Array or Object method implementations  Jeez     It certainly would be nice to have a single source of truth  but there isn t  Even if you ve been told otherwise  there is no Vanilla God  my dear  I m sorry  The only assumption that really holds is that we are all writing JavaScript code that aims at performing well in all major browsers  knowing that all of them have different implementations of the same things  It s a bitch to cope with  to put it mildly  But that s the premise  whether you like it or not  Maybe all of you are working on large scale projects that need twitterish performance so that you really see the difference between 850 000  Underscore js  vs  2 500 000  Lodash  iterations over a list per second right now  I for one am not  I mean  I worked on projects where I had to address performance issues  but they were never solved or caused by neither Underscore js nor Lodash  And unless I get hold of the real differences in implementation and performance  we re talking C   right now  of  let   s say  a loop over an iterable  object or array  sparse or not    I rather don t get bothered with any claims based on the results of a benchmark platform that is already opinionated  It only needs one single update of  let   s say  Rhino to set its Array method implementations on fire in a fashion that not a single  quot medieval loop methods perform better and forever and whatnot quot  priest can argue his her way around the simple fact that all of a sudden array methods in Firefox are much faster than his her opinionated brainfuck  Man  you just can t cheat your runtime environment by cheating your runtime environment  Think about that when promoting      your utility belt      next time  So to keep it relevant   Use Underscore js if you re into convenience without sacrificing native ish  Use Lodash if you re into convenience and like its extended feature catalogue  deep copy  etc   and if you re in desperate need of instant performance and most importantly don t mind settling for an alternative as soon as native API s outshine opinionated workarounds  Which is going to happen soon  Period  There s even a third solution  DIY  Know your environments  Know about inconsistencies  Read their  John-David s and Jeremy s  code  Don t use this or that without being able to explain why a consistency compatibility layer is really needed and enhances your workflow or improves the performance of your application  It is very likely that your requirements are satisfied with a simple polyfill that you re perfectly able to write yourself  Both libraries are just plain vanilla with a little bit of sugar  They both just fight over who s serving the sweetest pie  But believe me  in the end both are only cooking with water  There s no Vanilla God so there can t be no Vanilla pope  right   Choose whatever approach fits your needs the most  As usual  I d prefer fallbacks on actual implementations over opinionated runtime cheats anytime  but even that seems to be a matter of taste nowadays  Stick to quality resources like http   developer mozilla com and http   caniuse com and you ll be just fine

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I m agree with most of things said here  but I just want to point out an argument in favor of Underscore js  the size of the library  Specially in case you are developing an app or website which intend to be use mostly on mobile devices  the size of the resulting bundle and the effect on the boot or download time may have an important role  For comparison  these sizes are those I noticed with source-map-explorer after running Ionic serve  Lodash  523 kB Underscore js  51 6 kB  One can use BundlePhobia to check the current size of Lodash and Underscore js

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I created Lodash to provide more consistent cross-environment iteration support for arrays  strings  objects  and arguments objects1  It has since become a superset of Underscore js  providing more consistent API behavior  more features  like AMD support  deep clone  and deep merge   more thorough documentation and unit tests  tests which run in Node js  RingoJS  Rhino  Narwhal  PhantomJS  and browsers   better overall performance and optimizations for large arrays object iteration  and more flexibility with custom builds and template pre-compilation utilities  Because Lodash is updated more frequently than Underscore js  a lodash underscore build is provided to ensure compatibility with the latest stable version of Underscore js  At one point I was even given push access to Underscore js  in part because Lodash is responsible for raising more than 30 issues  landing bug fixes  new features  and performance gains in Underscore js v1 4 x   In addition  there are at least three Backbone js boilerplates that include Lodash by default and Lodash is now mentioned in Backbone js   s official documentation  Check out Kit Cambridge s post  Say  quot Hello quot  to Lo-Dash  for a deeper breakdown on the differences between Lodash and Underscore js  Footnotes   Underscore js has inconsistent support for arrays  strings  objects  and arguments objects  In newer browsers  Underscore js methods ignore holes in arrays   quot Objects quot  methods iterate arguments objects  strings are treated as array-like  and methods correctly iterate functions  ignoring their  quot prototype quot  property  and objects  iterating shadowed properties like  quot toString quot  and  quot valueOf quot    while in older browsers they will not  Also  Underscore js methods  like   clone  preserve holes in arrays  while others like   flatten don t

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In addition to John s answer  and reading up on Lodash  which I had hitherto regarded as a  quot me-too quot  to Underscore js   and seeing the performance tests  reading the source-code  and blog posts  the few points which make Lodash much superior to Underscore js are these   It s not about the speed  as it is about consistency of speed       If you look into Underscore js s source-code  you ll see in the first few lines that Underscore js falls-back on the native implementations of many functions  Although in an ideal world  this would have been a better approach  if you look at some of the performance links given in these slides  it is not hard to draw the conclusion that the quality of those  native implementations  vary a lot browser-to-browser  Firefox is damn fast in some of the functions  and in some Chrome dominates   I imagine there would be some scenarios where Internet  Explorer would dominate too   I believe that it s better to prefer a code whose performance is more consistent across browsers    Do read the blog post earlier  and instead of believing it for its sake  judge for yourself by running the benchmarks  I am stunned right now  seeing a Lodash performing 100-150  faster than Underscore js in even simple  native functions such as Array every in Chrome    The extras in Lodash are also quite useful  As for Xananax s highly upvoted comment suggesting contribution to Underscore js s code  It s always better to have GOOD competition  not only does it keep innovation going  but also drives you to keep yourself  or your library  in good shape   Here is a list of differences between Lodash  and it s Underscore js build is a drop-in replacement for your Underscore js projects

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If  like me  you were expecting a list of usage differences between Underscore js and Lodash  there s a guide for migrating from Underscore js to Lodash  Here s the current state of it for posterity    Underscore   any is Lodash   some Underscore   all is Lodash   every Underscore   compose is Lodash   flowRight Underscore   contains is Lodash   includes Underscore   each doesn   t allow exiting by returning false Underscore   findWhere is Lodash   find Underscore   flatten is deep by default while Lodash is shallow Underscore   groupBy supports an iteratee that is passed the parameters  value  index  originalArray   while in Lodash  the iteratee for   groupBy is only passed a single parameter   value   Underscore js   indexOf with third parameter undefined is Lodash   indexOf Underscore js   indexOf with third parameter true is Lodash   sortedIndexOf Underscore   indexBy is Lodash   keyBy Underscore   invoke is Lodash   invokeMap Underscore   mapObject is Lodash   mapValues Underscore   max combines Lodash   max  amp    maxBy Underscore   min combines Lodash   min  amp    minBy Underscore   sample combines Lodash   sample  amp    sampleSize Underscore   object combines Lodash   fromPairs and   zipObject Underscore   omit by a predicate is Lodash   omitBy Underscore   pairs is Lodash   toPairs Underscore   pick by a predicate is Lodash   pickBy Underscore   pluck is Lodash   map Underscore   sortedIndex combines Lodash   sortedIndex  amp    sortedIndexOf Underscore   uniq by an iteratee is Lodash   uniqBy Underscore   where is Lodash   filter Underscore   isFinite doesn   t align with Number isFinite  e g    isFinite  1   returns true in Underscore js  but false in Lodash  Underscore   matches shorthand doesn   t support deep comparisons  e g     filter objects     a      b    c        Underscore   1 7  amp  Lodash   template syntax is  template string  option  data  Lodash   memoize caches are Map like objects Lodash doesn   t support a context argument for many methods in favor of   bind Lodash supports implicit chaining  lazy chaining   amp  shortcut fusion Lodash split its overloaded   head    last    rest   amp    initial out into   take    takeRight    drop   amp    dropRight  i e    head array  2  in Underscore js is   take array  2  in Lodash

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For the most part Underscore js is subset of Lodash  At times  like presently  Underscore js will have cool little functions Lodash doesn t have  like mapObject  This one saved me a lot of time in the development of my project

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I am not sure if that is what OP meant  but I came across this question because I was searching for a list of issues I have to keep in mind when migrating from Underscore js to Lodash  I would really appreciate if someone posted an article with a complete list of such differences  Let me start with the things I ve learned the hard way  that is  things which made my code explode on production        flatten in Underscore js is deep by default  and you have to pass true as second argument to make it shallow  In Lodash it is shallow by default and passing true as second argument will make it deep       last in Underscore js accepts a second argument which tells how many elements you want  In Lodash there is no such option  You can emulate this with  slice   first  same issue    template in Underscore js can be used in many ways  one of which is providing the template string and data and getting HTML back  or at least that s how it worked some time ago   In Lodash you receive a function which you should then feed with the data    something  map foo  works in Underscore js  but in Lodash I had to rewrite it to   map something foo   Perhaps that was just a TypeScript-issue

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Lodash is inspired by Underscore js  but nowadays it is a superior solution  You can make your custom builds  have a higher performance  support AMD and have great extra features  Check this Lodash vs  Underscore js benchmarks on jsperf and    this awesome post about Lodash  One of the most useful feature when you work with collections  is the shorthand syntax  var characters          name    barney    age   36   blocked   false         name    fred      age   40   blocked   true          Using  quot   filter quot  callback shorthand   filter characters     age   36         Using Underscore js   filter characters  function character    return character age     36                 name    barney    age   36   blocked   false      taken from Lodash documentation

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They are pretty similar  with Lodash is taking over    They both are a utility library which takes the world of utility in JavaScript    It seems Lodash is getting updated more regularly now  so more used in the latest projects    Also Lodash seems is lighter by a couple of KBs    Both have a good API and documentation  but I think the Lodash one is better    Here is a screenshot for each of the documentation items for getting the first value of an array    Underscore js   Lodash   As things may get updated time to time  just check their website also    Lodash Underscore js

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I just found one difference that ended up being important for me  The non-Underscore js-compatible version of Lodash s   extend   does not copy over class-level-defined properties or methods  I ve created a Jasmine test in CoffeeScript that demonstrates this  https   gist github com softcraft-development 1c3964402b099893bd61 Fortunately  lodash underscore js preserves Underscore js s behaviour of copying everything  which for my situation was the desired behaviour

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Lodash has got   mapValues   which is identical to Underscore js s   mapObject

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Underscore vs Lo-Dash by Ben McCormick is the latest article comparing the two    Lodash s API is a superset of Underscore js s      Under the hood  Lodash has been completely rewritten      Lodash is definitely not slower than Underscore js      What has Lodash added      Usability improvements Extra functionality Performance gains Shorthand syntaxes for chaining Custom builds to only use what you need Semantic versioning and 100  code coverage

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