js原生 获取url参数

function GetQueryString(name) {   var reg = new RegExp("(^|&)" + name + "=([^&]*)(&|$)", "i");   var r = window.location.search.substr(1).match(reg);   var context = "";   if (r != null)      context = r[2];   reg = null;   r = null;   return context == null || context == "" || context == "undefined" ? "" : context;}