js 截取URL中的某个参数的值

function getQuerystring(key)
{
  //key = key.replace(/[\[]/,"\\\[").replace(/[\]]/,"\\\]");
  var regex = new RegExp("[\\?&]"+key+"=([^&#]*)&?",["i"]);
  var qs = regex.exec(window.location.href);
  if(qs == null)
    return '';
  else
    return qs[1];
}