TinyMCE is without a doubt one of the best WYSIWYG editor components that you can easily embed on your web applications.
If you check on the source code of TinyMCE in the official repository at Github, specifically on this file, you will find 2 properties on the definition of the TinyMCE object:
majorVersion: contains the Major version of TinyMCE build.
minorVersion: contains the Minor version of the TinyMCE build.
Knowing this, you may simply obtain the full version by concatenating the values like this:
// Prints 5.4.1 or your current version console.log(tinymce.majorVersion + '.' + tinymce.minorVersion);