Is it possible to execute javascript code on another page?

Question

JavaScript

Hello everyone :)
Please tell me how can I execute JavaScript code on another page? For example, insert a certain js code into the console in the browser, which should go to several pages in a row and fill out a form, etc. As I understand it, the js code only works on the page on which it is called, but maybe there is some way?) Well, or with the help of what web technologies is it possible to do this?)
Thank you very much in advance, I hope I expressed myself clearly :)

Answer 1

As an option, load the page code in a hidden iframe. And there it is already easy to access the elements through the iframe.