I'm practicing coding with some programming interview questions and finding Underscore.js helpful. Underscore is a utility-belt library for JavaScript with a bunch of commonly-needed functions. It has a couple of benefits that I can think of right away.
It can make code more readable. You can access the last element of an array with _.last(array), for example, instead of the clunky array[array.length - 1]. Also, having a bunch of utility functions at hand can free you to focus better on your current problem, too, instead of getting derailed by writing some simple function for the fiftieth time.