Question

Is there a way to access the DOM from the event fired by DOMContentLoaded?

window.addEventListener("load", function() { myExtension.init(); }, false);

var myExtension = {
  init: function() {
    var appcontent = document.getElementById("appcontent");   // browser
    if(appcontent)
      appcontent.addEventListener("DOMContentLoaded", myExtension.onPageLoad, true);
  },

  onPageLoad: function(aEvent) {
     //how to access to the DOM from aEvent??
  }, 
}

From https://developer.mozilla.org/en/Code_snippets/On_page_load

Answer 1

Just the first line in onPageLoad on the page you linked to shows how:

var doc = aEvent.originalTarget; // doc is document that triggered "onload" event

This gives you the document element of the website.