In rich web applications, we still want to provide linkable, bookmarkable, and shareable URLs to meaningful locations within an app.
Use the Router to update the browser URL whenever the user reaches a new "place" in your app that they might want to bookmark or share.
Events do not have to be declared before they are bound, and may take passed arguments.
For example: Bind a callback function to an object.
(Mimics of the Underscore and j Query APIs, such as Lodash and Zepto, will also tend to work, with varying degrees of compatibility.) When working on a web application that involves a lot of Java Script, one of the first things you learn is to stop tying your data to the DOM.