Why does the browser incorrectly perceive the encoding of the js file?

Question

JavaScript

Node v6.2 using gulp creates a js file, then sends it in the standard way via express

app.use('/public',express.static(__dirname + '/public'));

As far as I understand from the documentation, it should give it in utf-8 encoding, although the encoding is not specified in the browser header.
Content-Type: application/javascript
When I work directly with the server, the encoding is correctly recognized in any utf-8 browser, even if I specify in
<meta charset="window-1251">
But when I connect js to on another site, then the whole Russian language turns into cryosyabry and the browser accepts the js file in 125 encoding
. Everything revolves on СentOS, on which the default is also UTF-8

Answer 1

You can try to specify the encoding in the header
Content-Type: application/javascript; charset=utf8

Answer 2

If you add a BOM tag to the .js file, the browser will come to its senses and read the script as UTF8