AJAX responseXML 火狐

ajax.send(null);
		var arr = new Array(ajax.responseText);
		if(isIE){
			arr.push(ajax.responseXML.documentElement);
		}else{
			var parser = new DOMParser();
			xml = parser.parseFromString(ajax.responseText, "text/xml");
			arr.push(xml);
		}
		return arr;