In the html/css/js code editor, how does the js work even when no script is called?

Question

The js training is using the code editor for the “try it for yourself” training, but in the examples, the html page does not call any javascript. Is this an anomoly of Sololearn? Or does this happen in real life?

Answer 1

It doesn't need to be in the HTML page. You don't really even need any HTML for Javascript to work on some occasions.
Does this help?

Answer 2

Sometimes. Very rare that you need no html. If you are making a website or such, you need HTML Example
https://code.sololearn.com/W7Fol4hMQLp0/?ref=app

Answer 3

>>>It doesn't need to be in the HTML page. You don't really even need any HTML for Javascript to work on some occasions.
Does this help?<<< so on an html web page, with no html, where does the server or browser look for the .js file/code that needs executing?