Is it possible to use extended JS in the browser (as through the console)?

Question

JavaScript

You cannot call a loop in the console and write complex code. For example, I go to someone else's site, can I push my JS through the browser? For example, parse the page, etc.

Answer 1

You cannot call a loop in the console and write complex code.

Can.

push your JS through the browser

What problems? Create a tag scriptand upload whatever you want there.
But in general you need userscripts like tampermonkey .

Answer 2

You can write complex code in the console, hold down the shift key to break the line and only then press inter, but usually I use special browser extensions to run JavaScript on sites. Of course, you can also launch and parse through the console, but this is simply inconvenient.