How to get websocket data in json from a site?

Question

Node.js

You need to get data on currency pairs from a site that does not have an open API. I don’t understand a little how to do this, they write differently everywhere. I'm not asking for ready-made code, I need a trusted source where everything is explained in an accessible language, and of course your advice)

Answer 1

If there is no open API, then the site owners do not want anyone to use it without their permission. And this means that the CORS policy will not give you the ability to pull json (in the browser), and when you try to get it from the server (node.js), you will most likely need a secret key, or the server will refuse the request (due to an unresolved ip or other reasons).
Before starting such development, try to pull out the necessary json with the usual CURL