for (var i = 0; i < document.forms.length; i++) { var form = document.forms[i]; for (var j = 0; j < form.elements.length; j++) { var element = form.elements[j]; if (element.type == 'hidden' && element.name == 'inf_form_xid' && element.value == 'aa2ae350b1668a4a4cc80abc726fcfd9') { var input = document.createElement('input'); input.type = 'hidden'; input.id = 'timeZone'; input.name = 'timeZone'; input.value = Intl.DateTimeFormat().resolvedOptions().timeZone; form.appendChild(input); } } }