Infrequently Noted

The back button is one of those things that until recently I've considered an unfortunate casualty of the move from web pages to DHTML/CADEX applications. location.replace() and the history-less behavior of XMLHTTP have elicited foot-shuffling, eye-averting mumbling from people building responsive UIs when asked "what about the back button?". That the back button nukes all of a user's progress through an application has been a small point of collective shame. Wouldn't it be great if there were some way to cause the back-button to fire off some sort of callback within the UI instead of obliterating it?

Lo-and-behold, we have a solution! ()

Before I get into the nitty gritty of how this all works, let me provide a demonstration of the way you'd invoke this capability in Dojo. A normal call to get some data in Dojo often looks like:

dojo.io.bind({
  url: "sampleData.txt",
  load: function(type, data, evt){ alert(data); },
  error: function(type, errObj){ alert(errObj.message); }
});

dojo.io.bind({
  url: "sampleData.txt",
  load: function(type, data, evt){ alert(data); },
  error: function(type, errObj){ alert(errObj.message); },
  backButton: function(){ alert('the back button was intercepted, the document should not unload'); }
});