How to pass the Google Adwords gclid parameter onto your form confirmation page

unbounce-adwords-gclid.js

<script>
<!--
(function() {
  function getQueryParam(paramName) {
    var query = window.location.search;
    var paramValue = null;
    var pos = query.indexOf(paramName + '=');
    if (pos > -1) {
      var start = pos + paramName.length + 1;
      var end = query.indexOf('&', start);
      end = end > -1 ? end : query.length;
      paramValue = query.substring(start, end);
    }
    return paramValue;
  }

  var gclid = getQueryParam("gclid");
  if (gclid != null) {
    var previous_form_url = 
      window.module.lp.form.data['confirmData'];
    window.module.lp.form.data['confirmData'] = 
      previous_form_url + "?gclid=" + gclid;
  }
}) ();
-->
</script>

A shorter alternative to getQueryParam that I use sometimes is:

var getQueryParam = function(name){
  var results = new RegExp('[\\?&]' + name + '=([^&#]*)').exec(window.location.href);
  return results ? (results[1] || null) : null;
}

Yeah, that's certainly more compact and covers more cases. Is window.location.href more widely supported than window.location.search?

Good question - I can't see any reason not to use location.search instead of location.href -- no difference in support across browsers as far as I know.