1 files changed, 19 insertions, 1 deletions
diff --git a/web_src/js/features/common-global.js b/web_src/js/features/common-global.js
index a9baf9be0c..60af4d0d67 100644
--- a/web_src/js/features/common-global.js
+++ b/web_src/js/features/common-global.js
@@ -3,8 +3,9 @@ import 'jquery.are-you-sure';
 import {mqBinarySearch} from '../utils.js';
 import createDropzone from './dropzone.js';
 import {initCompColorPicker} from './comp/ColorPicker.js';
+import {showGlobalErrorMessage} from '../bootstrap.js';
 
-const {csrfToken} = window.config;
+const {appUrl, csrfToken} = window.config;
 
 export function initGlobalFormDirtyLeaveConfirm() {
   // Warn users that try to leave a page after entering data into a form.
@@ -343,3 +344,20 @@ export function initGlobalButtons() {
     });
   });
 }
+
+/**
+ * Too many users set their ROOT_URL to wrong value, and it causes a lot of problems:
+ *   * Cross-origin API request without correct cookie
+ *   * Incorrect href in <a>
+ *   * ...
+ * So we check whether current URL starts with AppUrl(ROOT_URL).
+ * If they don't match, show a warning to users.
+ */
+export function checkAppUrl() {
+  const curUrl = window.location.href;
+  if (curUrl.startsWith(appUrl)) {
+    return;
+  }
+  showGlobalErrorMessage(`Your ROOT_URL in app.ini is ${appUrl} but you are visiting ${curUrl}
+You should set ROOT_URL correctly, otherwise the web may not work correctly.`);
+}