After CSS and HTML is it necessary to learn JS or I can learn sth like Py?

Answer 1

Js is not only a backend language. It is also a very effective front end language, so although it is not compalsary to learn JS but it is recommended.

Answer 2

Well, if you want to pursue web development its necessary learn JS and then php and then other JS frameworks like node.js, angular, react, etc
Else, your choice.