How can you redesign a website without direct access to it?

Question

JavaScript

Hello.
In general, the task is to make a mobile application (WebView) without interfering with the code and structure of the site.
In what ways (technologies) is it possible to implement this?

Answer 1

1. Take data from the API, if any.
2. Parse the old fashioned way.
*Slowly I catch dissonances from the question and the author's signature*