Underscore.js
Underscore is a JavaScript library which provides utility functions for common JavaScript tasks. It is comparable to features provided by Prototype.js and the Ruby language, but opts for a functional programming design instead of extending object prototypes. For example, underscore's _.each function delegates to the host environment's native forEach implementation when present, or a compatible version when absent. The documentation refers to Underscore as "the tie to go along with jQuery's tux, and Backbone.js's suspenders." Underscore was created by Jeremy Ashkenas, who is also known for Backbone.js and CoffeeScript.[1]