The examples I\'ve seen online seem much more complex than I expected (manually parsing &/?/= into pairs, using regular expressions, etc). We\'re using asp.net
If there's any possibility of encountering repeated parameters (e.g. ?tag=foo&tag=bar), most libraries out there won't be sufficient. In that case, you might want to consider this library that I developed from Jan Wolter's very comprehensive parser. I added .plus() and .minus() functions and roundtripping:
https://github.com/timmc/js-tools/blob/master/src/QueryString.js