Simple addEventListener polyfill for IE8

addeventlistener.js

( function( win, doc, s_add, s_rem ) {
	if( doc[s_add] ) return;
	Element.prototype[ s_add ] = win[ s_add ] = doc[ s_add ] = function( on, fn, self ) {
		return (self = this).attachEvent( 'on' + on, function(e){
			var e = e || win.event;
			e.target = e.target || e.srcElement;
			e.preventDefault  = e.preventDefault  || function(){e.returnValue = false};
			e.stopPropagation = e.stopPropagation || function(){e.cancelBubble = true};
			e.which = e.button ? ( e.button === 2 ? 3 : e.button === 4 ? 2 : e.button ) : e.keyCode;
			fn.call(self, e);
		});
	};
	Element.prototype[ s_rem ] = win[ s_rem ] = doc[ s_rem ] = function( on, fn ) {
		return this.detachEvent( 'on' + on, fn );
	};
})( window, document, 'addEventListener', 'removeEventListener' );