javascript得到url的参数的值

//得到url的参数的值
function getQueryString(queryStringName)
{
 var returnValue="";
 var URLString=new String(document.location);
 var serachLocation=-1;
 var queryStringLength=queryStringName.length;
 do
 {
  serachLocation=URLString.indexOf(queryStringName+"\=");
  if (serachLocation!=-1)
  {
   if ((URLString.charAt(serachLocation-1)=='?') || (URLString.charAt(serachLocation-1)=='&'))
   {
    URLString=URLString.substr(serachLocation);
    break;
   }
   URLString=URLString.substr(serachLocation+queryStringLength+1);
  }
 
 }
 while (serachLocation!=-1)
 if (serachLocation!=-1)
 {
  var seperatorLocation=URLString.indexOf("&");
  if (seperatorLocation==-1)
  {
   returnValue=URLString.substr(queryStringLength+1);
  }
  else
  {
   returnValue=URLString.substring(queryStringLength+1,seperatorLocation);
  }
 }
 return returnValue;
}