//First we must call the EnsureSetup method
JSRequest.EnsureSetup();
//Get a query string parameter
var var1= JSRequest.QueryString["var1"];
var var2 = JSRequest.QueryString["var2"];
document.write( var1+ ”);
document.write(var2);

The JSRequest class is a JavaScript object that lives on all SharePoint Pages, and allows us to simply and quickly get query string parameters using JavaScript.

It has 3 fields: QueryString, FileName, and PathName.

QueryString – is an array of key\value pairs representing the current query string parameters.
FileName – is a string containing the current name of the current page.
PathName – is the server relative path of the current page.

if your query string is “?letter=A&list=123456-1234-1234-1234″

“location.search” would return “?letter=A&list=123456-1234-1234-1234″

“locaton.search.substring(1)” would return “letter=A&list=123456-1234-1234-1234″ (i.e. without the leading “?”)

“getQueryParam(‘letter’)” would return “A”

As you’re needing to pass the entire query string, location.search.substring(1) is fine – but all I wanted was a single value from the query string.

You migt also find this interesting:
http://www.novolocus.com/2009/05/15/get-query-string-parameters-with-regular-expressions-in-javascript/

(Same function really, but I keep having to tell people to do it this way if you only want one or two query string parameters)

I had a request to pass parameters to the url of an iFrame embedded in my layout page. I had to accept whatever parameters were sent so I needed to grab the entire query string and append it.

This worked fine for me; though I’m a newbie and now you have me second guessing myself?