With modern IDEs, it is possible for a developer to open a file by typing just a few characters of that file's name. This feature, along with a general desire to keep code organized, has motivated developers to separate their code into multiple files. In Backbone, this typically means creating one file for every Collection, Model, View, and Router, and even in a small project, this can add up to a lot of files.

All these files create two problems. First, each file needs to be downloaded separately, and as we learned in Chapter 8, Scaling Up: Ensuring Performance in Complex Applications, browsers can only download between 2 and 8 files at once. Second, the order in which files are loaded can become increasingly hard to manage, because of the dependencies among the different files (View A needs Collection B, which needs Model C, which needs …). RequireJS (http://requirejs.org/) solves both of these problems.

RequireJS does this by organizing your code into...