In addition to John's answer, and reading up on Lodash (which I had hitherto regarded as a "me-too" 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.
