OpenLayers provides an easy way to configure the library file that gets included in your page. Throughout the book, we've been including a file called OpenLayers.js, which is a file that contains all the functionality (classes, functions, and so on) that OpenLayers provides. So far, this has been great—we've been developing up to this point, so we want to be sure that we have access to all the classes that we may use. What's my point here?
Well, the OpenLayers.js file we've been using is around 920 KB! That's almost a megabyte—quite a large file to load, especially since it contains only JavaScript code. Even though large file sizes aren't as much of an issue as they were years ago, when everyone was on slower connections, a one megabyte JavaScript file in a production environment is something we want to avoid if at all possible.
We want all our files in a production environment to be as small as they can absolutely be. This...