All is described in this tutorial https://www.cmscanbesimple.org/blog/easy-way-to-combine-and-minify-javascript-files-and-code

Thanks for your quick reply, i see your test, it's ok
So strange i don't understand the problem in my case... have you any .htaccess rules overwritting the default ?
I'm using php 7.0.22 and you ?
Have you a config.php with extended options ?
I try to find a solution.
Thanks and have a good day.

I did a quick test and it works for me:
https://www.cmscanbesimple.org/page.js

++++++++++++++++++++++++++++++++++
{content_type type='text/javascript'}

$(document).ready(function() {
$('#slider').cycle( {
delay: -2000,
timeout: 6000,
speed: 2000,
pause: 1
} );
} );

++++++++++++++++++++++++++++++++++

Hello Rolf,
I just install the version 2.2.3.1, and i'm not succeed to do that (but it was working since several years with 1.11.x and 1.12.x with a similar solution)
The page doesn't render, CMSMS do like the "page.js" doesn't exist, i do the minimal :
Gabarit "minimal" : {content}
"page.js" with "minimal" : few lines of javascript code with UDT "content-type" in first line
UDT "content-type" : cmsms()->set_content_type('text/javascript');
Config CMSMS :
....
$config['url_rewriting'] = 'mod_rewrite';
#$config['page_extension'] = '.html';
#$config['default_encoding'] = 'utf-8';
...

I have no error in Apache logs... i use php 7.0 on a Ubuntu 16.04 VM
If you have an explication, i will take it ;o)... thanks a lot in advance.