Get query string parameters using a Java Script

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

//Call the function
var CategoryID = getQuerystring('CategoryIDs');