code: function (id) {
      /* Get the corresponding html element. */
      var domelt = document.querySelector(id);
      if (!domelt) {
        return { on: function () {} };
      }
  
      /* Now that we have the elt and onprop, assign it. */
      domelt.on = onprop;
      return domelt;
    }
docs: /* End of "on" property.