Search and replace specific query string parameter value in javascript

Question

I have a string which is something like this :

a_href= "www.google.com/test_ref=abc"; 

I need to search for test_ref=abc in thisabove strinng and replace it with new value

var updated_test_ref = "xyz";  a_href ="www.google.com/test_ref=updated_test_ref"  

i.e

www.google.com/test_ref=xyz. 

How can we do this ?

EDIT:

test_ref value can be a URL link in itself something like http://google.com?param1=test1&param2=test2. I need to capture complete value not till first &.

Answer 1

a_href = a_href.replace(/(test_ref=)[^\&]+/, '$1' + updated_test_ref); 

Answer 2

Based on this discussion I have fixed the Chris function (problem with regex string!)

function updateUrlParameter(url, param, value){     var regex = new RegExp('('+param+'=)[^\&]+');     return url.replace( regex , '$1' + value); }