How to fix problem with relative path Joomla for a module using editor form field?

I've now discovered that I need to insert a slash in front of the URL to load from the root directory. For example: /joomla-cms/images/joomla_black.png.

This is not good because many editors simply delete this slash. Also, the URL is not really relative anymore. It can not be easily used in a subdirectory anymore - for example in an test envirement with xampp.

Then I found out that the Joomla SEF system plugin could not be activated. That plugin is for does checking and correction the relative path. This was not the problem for me either. The plugin was active. In my case, the plugin has been bypassed because I use the input in JavaScript.

Therefore, I change now the editor input in my JavaScript file myself. I store the URL before in php.

<div data-uriroot='<?php echo JUri::root(); ?>'></div>

Then I paste this line in JavaScript.

var uriroot = element.getAttribute('data-uriroot');
...
MEINE_DITORTEXT.replace(/<img src="images/g, '<img src="' + uriroot + 'images')

Maybe another person might need it?