Callbacks vs Events

Dean Edwards points out that using an array and looping through callbacks is brittle:

$(document).ready(function() {
  console.log("Init: 1");
  DOES_NOT_EXIST++; // this will throw an error
});

$(document).ready(function() {
  console.log("Init: 2");
});</pre>

What do we see in the console?

Init: 1

Error: DOES_NOT_EXIST is not defined

The problem is clear. Callback systems are brittle. If any of the callback functions throws an error then the subsequent callbacks are not executed. In reality, this means that a poorly written plugin can prevent other plugins from initialising.