Use Intl.DateTimeFormat() to set timezone cookie (#1794)

* Use  Intl.DateTimeFormat() to set timezone cookie

* Fix timezone cookie check

funnel/assets/js/app.js

@@ -1,7 +1,5 @@
 import 'jquery-modal';
 import 'trunk8';
-import jstz from 'jstz';
-import 'jquery.cookie';
 import Utils from './utils/helper';
 import WebShare from './utils/webshare';
 import ScrollHelper from './utils/scrollhelper';
@@ -14,6 +12,7 @@ import updateParsleyConfig from './utils/update_parsley_config';
 import ReadStatus from './utils/read_status';
 import LazyLoadMenu from './utils/lazyloadmenu';
 import './utils/getDevicePixelRatio';
+import setTimezoneCookie from './utils/timezone';
 import 'muicss/dist/js/mui';
 
 const pace = require('pace-js');
@@ -63,11 +62,7 @@ $(() => {
     document.head.appendChild(polyfill);
   }
 
-  // Detect timezone for login
-  if (!$.cookie('timezone')) {
-    $.cookie('timezone', jstz.determine().name(), { path: '/' });
-  }
-
+  setTimezoneCookie();
   updateParsleyConfig();
 });
 

funnel/assets/js/utils/timezone.js

@@ -0,0 +1,15 @@
+import 'jquery.cookie';
+
+// Detect timezone for login
+async function setTimezoneCookie() {
+  if (!$.cookie('timezone')) {
+    let timezone = Intl.DateTimeFormat()?.resolvedOptions()?.timeZone;
+    if (!timezone) {
+      const { default: jstz } = await import('jstz');
+      timezone = jstz.determine().name();
+    }
+    $.cookie('timezone', timezone, { path: '/' });
+  }
+}
+
+export default setTimezoneCookie;