How to extract URL search parameters

Extracting a single parameter

If you require a one off extraction of a few parameters, this function will suffice.

function Param(a)
{
   var m = location.search;

   if (m && (m = m.match('[?&]' + a + '=([^&]*)')))
      return decodeURIComponent(m[1]);
}

Extracting all parameters

This function extracts all the parameters into an object for easy access.

Example usage

<!DOCTYPE html>

<html>
<body>
   <script>
   function Param(a)
   {
      var m = location.search;

      if (m && (m = m.match('[?&]' + a + '=([^&]*)')))
         return decodeURIComponent(m[1]);
   }

   function Params()
   {
      var m = location.search, p = {}, i, n;

      if (m && (m = m.match(/[?&][^=]*|=[^&]*/g)))
      {
         n = m.length;

         for (i = 0; i < n; i += 2)
            p[m[i].substr(1)] = m[i + 1] != '=' ? decodeURIComponent(m[i + 1].substr(1)) : '';
      }

      return p;
   }

   params = Params();

   alert(
      'def = "' + Param('def') + '" ' +
      'bc = "' + params.bc + '" ' +
      'z = "' + params.z + '"'
   );
   </script>
</body>
</html>

Launching the above code with a search string of ?a=1&bc=%2Fp%20%2Fq&def=p%26q%3F&y=&z=last will display:

def = "p&q?"

bc = "/p /q"
z = "last"