How to run code from browser debugger?

Question

Browsers

Here is a site. I need to make changes to it. I do not have access to the site. How to make changes, for example, in a js file?
1. Open the developer panel.
2. Add code to the js file
... And then how? Run this case with changes and see the result?

Answer 1

Put an extension that can connect your own css and js and add code through it. And since you want it will not work.
If you just want to replace the js file, then you need to look not in the direction of the browser, but in the direction of the proxy. For example, privoxy does a great job with this. But the site must be accessible via http, of course.