JS获取网址中指定值的正则函数

<script type="text/javascript"> 
String.prototype.getQuery = function(name){ 
var reg = new RegExp('(^|\\?|&)'+name+'=([^&]*|$)'), url = this.replace(/&/g, '&'), r = url.match(reg); 
return r === null ? null : unescape(r[2]); 
} 
var str = 'http://wpa.qq.com/msgrd?v=3&uin=1438344583&site=qq&menu=yes'; 
alert(str.getQuery('uin')); 
</script>