WordPress: prevent caching of tinymce’s custom buttons?

I’m following this tutorial on how to add a custom button to TinyMCE editor in WordPress. Trying to edit author’s JS to include my functionality, yet it seems to have gotten cached. Article author has a hack for it (code snippet below), and it did work for the first time (the button is in the toolbar now), although it doesn’t work for subsequent refreshes.

// "This will intercept the version check and increment the current version number by 3.
// It's the quick and dirty way to do it without messing with the settings directly..."
function my_refresh_mce($ver) {
  $ver += 3;
  return $ver;
}

add_filter( 'tiny_mce_version', 'my_refresh_mce');

What can I do to disable this caching?

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