Adding multiple onload handlers

Question

I have two js files, each one with its own window.onload handler. Depending on how I attach the two onload handlers to the window object I get a different behaviour on the s

Answer 1

Just in case future people find this, and are looking for a way to use multiple event handlers when the object itself doesn't support addEventListener, attachEvent or some other form of listener stacking - i.e. it is a bespoke object, badly implemented. Then you can do the following:

object.onload = (function(pre){
  return function(){
    pre && pre.apply(this,arguments);
    /// do what you need for your listener here
  }
})(object.onload);

Each time you use the above code the previous onload listener is passed in as an argument, and when your new listener is triggered it runs the old listener first - meaning you can stack many listeners like this, if you so wish. However, this will only work for as long as the above code is always used to add listeners to your object. All your hard work will be undone if somewhere else it is overridden with a simple:

object.onload = function(){}

As a note to coders, if you are to implement a library, plugin or constructor, and it is possible other coders will take over your work. Please, please code the ability for multiple event listeners. It's really not that difficult.