Add multiple window.onload events

Question

In my ASP.NET User Control I'm adding some JavaScript to the window.onload event:

if (!Page.ClientScript.IsStartupScriptRegistered(this.GetType(), onloadScriptName))
  Page.ClientScript.RegisterStartupScript(this.GetType(), onloadScriptName, 
    "window.onload = function() {myFunction();};", true);            

My problem is, if there is already something in the onload event, than this overwrites it. How would I go about allowing two user controls to each execute JavaScript in the onload event?

Edit: Thanks for the info on third party libraries. I'll keep them in mind.

Answer 1

Most of the "solutions" suggested are Microsoft-specific, or require bloated libraries. Here's one good way. This works with W3C-compliant browsers and with Microsoft IE.

if (window.addEventListener) // W3C standard
{
  window.addEventListener('load', myFunction, false); // NB **not** 'onload'
} 
else if (window.attachEvent) // Microsoft
{
  window.attachEvent('onload', myFunction);
}