While Underscore is a powerful library and in the same time, it is a relatively small one that has around 1,500 lines of code. You can read through its annotated source code available at http://underscorejs.org/docs/underscore.html in less than an hour (if you are an experienced JavaScript developer).

Many popular JavaScript libraries have a similar size and when they become bigger they are split into separate components. These bigger libraries provide some core functionality as a main component and provide further specialized functionality in optional packages.

Underscore-contrib is a functional library that is closely related to Underscore as its official companion or complementary library. The Underscore-contrib source code and documentation are hosted by the same parent organization of Underscore, although a different author created it originally.

Similar to Underscore, it has great documentation and annotated source code available at http://documentcloud...