title: How does Gmail handle back/forward in rich JavaScript?
body: <p>Gmail seems to have some clever way of handling the back/forward buttons in a rich JS application.</p>
  
  <p>In my organisation we trialled the jQuery history plugin. The plugin basically runs a function every 100ms which parses the URL and tests if it has changed. The history is tracked by HTTP anchors, and if the anchor has changed then the plugin calls a user-specified callback, passing in the new anchor, so that the page can perform custom behaviour to load in the new content.</p>
  
  <p>My organisation determined that the jQuery history plugin was not production quality. I don't blame them to be honest, because you don't really want to force your users' browsers to run a function every 100ms. Also, it made the JS code almost impossible to debug, because clicking "Break On Next" in Firebug or similar JS debugger, would always trap the jQuery history event, and no other events would get a look in.</p>
  
  <p>So we gave up at this point on implementing back/forward functionality in the browser. However, I've recently noticed that Gmail implements this rather nicely. It also uses the HTTP anchor value, but I pressed "Break On Next" and Gmail doesn't run any kind of function every 100ms. How does Gmail manage to implement this back/forward behaviour?</p>