Research in the comments revealed that the browser’s cache is to blame.
Cache can be cleaned by hand, the usual shortcuts are as follows:
1. Ctrl + F5 - page reload without cache
2. Ctrl + Shift + Delete - select "cache".
For development purposes in Chrome Dev Tools (and probably in similar tools from other browsers) there is a setting:
F12 - open devtools
Three points on the top right of the devtools (menu " Customize and control devtools ") - Settings
Left Tab Preferences
Networks group
Galka Disable cache (while DevTools is open)
This is all for development purposes, if we need the file not to be cached for the final user, usually the correct http-headers are set and new parameters are added to the resource request, but this is a separate long story.