jQuery 4.0 compatibility: $.isFunction is not a function

Problem/Motivation

The field_timer module uses jQuery's countdown plugin which relies on $.isFunction() method. This method was removed in jQuery 3.3+ and causes errors when used with jQuery 4.0+.

Error:

Uncaught TypeError: a.isFunction is not a function
  at d._adjustSettings (jquery.countdown.js:488:27)
  at field_timer.js:30:23

Affected Code: field_timer/js/field_timer.js lines 28-50 (countdown plugin initialization)

Root Cause: The countdown plugin internally uses $.isFunction() which was removed from jQuery 3.3+

Steps to Reproduce

1. Install field_timer module on a site with jQuery 4.0+
2. Add a countdown field to any content type
3. Create content with the countdown field
4. View the content page
5. Check browser console (F12)
6. See error: "TypeError: a.isFunction is not a function"

Proposed Resolution

Add a jQuery compatibility polyfill to the beginning of field_timer.js that restores missing jQuery methods ($.isFunction, $.isWindow, $.isArray, etc.) for compatibility with jQuery 4.0+.

The polyfill:

• Checks if methods exist before overriding
• Uses native JavaScript equivalents
• Logs success/errors to console
• Has no performance impact on newer jQuery versions
• Allows older plugins to work with modern jQuery

Remaining Tasks

1. Review the proposed patch
2. Test with jQuery 3.x and 4.x versions
3. Merge patch into next release