Learn Underscore.js by focusing on each of the Underscore functions to learn to manipulate and control javascript collections, arrays, objects and functions. See how Underscore can significantly improve the performance of your code and how to the functional nature of the library can help make your code more expressive and easier to read. The last module of the course demonstrates how to use Underscore in an integration exercise to create aggregations, data manipulations, integrate with a ViewModel and extend the library to add your own functionality.