Best way to concatenate two URL parameters into one hidden field

Best way to concatenate two URL parameters into one hidden field

How can I concatenate two URL parameters into one hidden field? For example:

sometestingurl.com?color=yellow&thingy=box

We'd like "yellow-box" to pass in the hidden field, "finalProd".

  2.     $('a[href^="http"]').each(function() {
  3.         var $a = $(this),
  4.             q = $a.attr('href') ? $a.attr('href').indexOf('?') : -1,
  5.             contents = $a.html();
  6.         if (q == -1) {
  7.             $a.attr('href', $a.attr('href') + '?color=' + App.getParameterByName('color') + '&thingy=' + App.getParameterByName('thingy'));
  8.         } else {
  9.             $a.attr('href', $a.attr('href') + '&color=' + App.getParameterByName('color') + '&thingy=' + App.getParameterByName('thingy'));
  10.         }
  11.         $a.html(contents);
  12.     });
  13.     var color = $("#color").attr('value', App.getParameterByName('color'));
  14.     var thingy = $("#thingy").attr('value', App.getParameterByName('thingy'));
  15.     $("#finalProd") = color + '-' + thingy;
Within the form...
  1. <input type="hidden" name="finalProd" id='finalProd' value="">