docs: function getParameterValue(key, opt_uri) {
    var uri = opt_uri || window.location.href;
    key = key.replace(/[\[]/, '\\\[').replace(/[\]]/, '\\\]');
    var regex = new RegExp('[\\?&]' + key + '=([^&#]*)');
    var results = regex.exec(uri);
    var result = results === null ? null : results[1];
    return result ? urlDecode_(result) : null;
  }