I'm trying to parse a Parameter value from the Query String in JavaScript

E.g URLs: 

http://www.contoso.com?key1=value1&key2=value2

http://www.contoso.com?&key2=value2&key1=value1

 [window.location.search.substring(0) in JS automatically return portion after '?' so i just need to parse out the key-value]

Result (in both cases)

value1 (If i look up param 'key1') 

I have the following  in Javascript but it does not work for all

 var match = /(?:\?|&)RU=(\S+)(&(\S+)*)/i.exec(window.location.search.substring(0));

Please help

 
-A