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(/&amp;/g, '&'), r = url.match(reg);
return r === null ? null : unescape(r[2]);
}
var str = 'http://wpa.qq./msgrd?v=3&amp;uin=1438344583&amp;site=qq&amp;menu=yes';
alert(str.getQuery('uin'));
</script>