John Resig's on/off (aka addEventListener)

events.js

  function on(obj, type, fn) {
    if (obj.attachEvent) {
      obj['e'+type+fn] = fn;
      obj[type+fn] = function(){ obj['e'+type+fn]( window.event ); };
      obj.attachEvent( 'on'+type, obj[type+fn] );
    } else {
      obj.addEventListener( type, fn, false );
    }
  }
  function off(obj, type, fn) {
    if (obj.detachEvent) {
      obj.detachEvent('on'+type, obj[type+fn]);
      obj[type+fn] = null;
    } else {
      obj.removeEventListener(type, fn, false);
    }
  }