problems with file:/// URLs

[scorpi11]

I have a website which works when I use it via HTTPS. However, it is broken when I use the same website via file:///. This is a new problem that did not occur ~3 weeks ago.

It works fine when I disable NoScript.

Only a part of the JavaScript seems to work and I see JavaScript error messages that don't make sense, like an undefined variable which is clearly defined:

HTML code:

<script type='text/javascript' >
    var currentIndex = 1;
</script>

JavaScript error:

Uncaught ReferenceError: currentIndex is not defined

Other errors indicate that a script is executed twice for some reason:

Uncaught SyntaxError: redeclaration of const gallery_data