javascript获取URL参数

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;
}