WordPress 3.5 Admin Error: “jQuery is not  defined”

Today is the big day, I’ve begun upgrading various installs to WordPress 3.5. Many of them have been experiencing issues with JavaScript related errors in the admin. WordPress 3.5 has a new performance loading feature that will concatenate all JavaScript resources into a single request (which is awesome).

Unfortunately this new method currently caused conflicts with many heavily used plugins, and I’ve been seeing many jQuery is not defined and Uncaught ReferenceError: jQuery is not defined errors in my JavaScript console. Luckily, there’s a simple fix.

The Solution

SSH or FTP into your site and open up your wp-config.php file. Turn off script concatenating by adding this line:

define('CONCATENATE_SCRIPTS', false);

Make sure you add this before:

/** Absolute path to the WordPress directory. */
if ( !defined('ABSPATH') )
        define('ABSPATH', dirname(__FILE__) . '/');

Hopefully this helps you save the day for your WordPress installs!