add/remove event with handleEvent helper

add-event.js

// modified John Resig's http://ejohn.org/projects/flexible-javascript-events/

var div = document.createElement('div');

var addEvent, removeEvent;

if ( div.addEventListener ) {
  addEvent = function( elem, type, fn ) {
    elem.addEventListener( type, fn, false );
  };
} else if ( div.attachEvent ) {
  // <= IE8
  addEvent = function( elem, type, fn ) {
    var onFn = fn;
    // handleEvent fill
    if ( fn.handleEvent ) {
      onFn = function( event ) {
        fn.handleEvent.call( fn, event );
      };
    }
    // hash original function
    elem[ 'e' + type + fn ] = onFn;
    // hash this function so we can remove it
    elem[ type + fn ] = function() {
      elem[ 'e' + type + fn ]( window.event );
    };
    elem.attachEvent( "on" + type, elem[ type + fn ] );
  };
}


if ( div.removeEventListener ) {
  removeEvent = function( elem, type, fn ) {
    elem.removeEventListener( type, fn, false );
  };
} else if ( div.detachEvent ) {
  // <= IE8
  removeEvent = function( elem, type, fn ) {
    elem.detachEvent( "on" + type, elem[ type + fn ] );
    // delete references
    delete elem[ type + fn ];
    delete elem[ 'e' + type + fn ];
  };
}