Important: #79221 - Use $ instead of TYPO3.jQuery 

See forge#79221

Description 

The TYPO3 Core uses jQuery in the TYPO3 Backend with a default namespace of TYPO3.jQuery and jQuery in the global object namespace, and is now also available as global $ when no other namespace is given. This was not possible before due to conflicts with prototype.js.

If using the shipped jQuery code in the Frontend explicitly via page.javascriptLibs.jQuery.noConflict.namespace = default then the global $ is also available in frontend scripts.