remove all empty values from url

Something like this:

s = s.replace(/[^=&]+=(&|$)/g,"").replace(/&$/,"");

That is, remove groups of one or more non-equals/non-ampersand characters that are followed by an equals sign and ampersand or end of string. Then remove any leftover trailing ampersand.

Demo: http://jsfiddle.net/pKHzr/

s = s.replace(/[^?=&]+=(&|$)/g,"").replace(/&$/,"");

Added a '?' to nnnnnn's answer to fix the issue where the first parameter is empty in a full URL.