JavaScript error when js-cookie library is not loaded

Problem/Motivation

The modal-page.js file throws a JavaScript error when the js-cookie library (exposed as window.Cookies) is not loaded or available:

Uncaught TypeError: Cannot read properties of undefined (reading 'remove')
    at HTMLDivElement.<anonymous> (modal-page.js:60:19)

This occurs because the code attempts to call methods on the cookies object without first checking if it exists. The cookies parameter is passed from window.Cookies, which may be undefined if:

• The js-cookie library hasn't been loaded yet
• The library failed to load
• The library is not included in the page

This error can break other JavaScript on the page and prevent the modal from functioning properly.

Steps to reproduce

1. Install the Modal Page module
2. Configure a modal page
3. Ensure the js-cookie library is not loaded or fails to load
4. Load a page that should display the modal
5. Open browser console
6. Observe the JavaScript error: Cannot read properties of undefined (reading 'remove')

Proposed resolution

Add null/undefined checks before using the cookies object in all locations where it's accessed. This ensures the code gracefully handles the case when the js-cookie library is not available.

Code changes needed:

1. Line 60: Add check before calling cookies.remove()
2. Line 64: Add checks before calling cookies.get() (both calls)
3. Line 91: Add check before calling cookies.set() in the hide event handler
4. Line 202: Add check before calling cookies.set() in the click handler

// Remove the cookie if show only once option is disabled.
- if (show_once != "1") {
+ if (show_once != "1" && cookies) {
    cookies.remove('hide_modal_id_' + id_modal);
  }

// Get cookies for do not show again option and show only once.
- var hide_modal_cookie = cookies.get('hide_modal_id_' + id_modal) || cookies.get('please_do_not_show_again_modal_id_' + id_modal);
+ var hide_modal_cookie = (cookies && cookies.get('hide_modal_id_' + id_modal)) || (cookies && cookies.get('please_do_not_show_again_modal_id_' + id_modal)) || null;

modal.on('hide.bs.modal', function () {
-   if (show_once == "1") {
+   if (show_once == "1" && cookies) {
      cookies.set('hide_modal_id_' + id_modal, true, { expires: 365 * 20, path: '/' });
    }
});

ok_button.on('click', function () {
-   if (checkbox_please_do_not_show_again.is(':checked')) {
+   if (checkbox_please_do_not_show_again.is(':checked') && cookies) {
      // ... cookie setting code
    }
});

Expected behavior after fix:

The code should gracefully handle the case when the cookies object is undefined. Cookie functionality should be skipped if the library is not available, but the modal should still function without throwing errors.

Remaining tasks

• Review and test the proposed fix
• Ensure backward compatibility (modal should still work when cookies library is available)
• Update documentation if needed

User interface changes

None. This is a bug fix that prevents JavaScript errors. No UI changes are required.

API changes

None. No API changes are required.

Data model changes

None. No data model changes are required.