JavaScript - Extracting variable from string

[Datacide]

I have the following code which works awesome for getting the variables form the URL:

function $_GET(q,s) {
  s = (s) ? s : window.location.search;
  var re = new RegExp('&'+q+'=([^&]*)','i');
  return (s=s.replace(/^\?/,'&').match(re)) ? s=s[1] : s='';
}

document.getElementById(RefId).value = $_GET('refcode');

But it doesn't work if I use document.referrer instead of window.location

If I place window.location into a string and use the string in the function it works. If I place document.referrer in a string and use the string in the function it doesn't work.

The values of window.location is

http://site.org/Default.aspx?refcode=12345&pageId=890916

The value of document.referrer is

http://site.org/bluepage.html?refcode=12345

Any thoughts?