To start with - a lot of functions to help the developers build better applications - if your website has a lot of data to handle and a lot of client side processing and computations, you probably want to use a library that will help you do those computations and handle the data very easily and conveniently - There is a vast inner world in underscore, to categorize, there are collections, arrays, functions, objects, utility and chaining - each of the categories has a wide range of functions, not limited to: search, sort, find at index, math functions, etc. - if you can code one of the languages such as Java or C with proficiency, you will get along with underscore pretty nicely

All of the functions dealing with collections are tremendously useful.

I love how easy it is to map arrays to destination objects, and also there are nice filter and find functions available.