But I tough that javascript could also be written in a separate .js file, later included in .html page, not only in head and body tags.

Answer 1

You're correct. Having JavaScript code in an external file is preferred especially if the same code is included in more than one HTML document.

Answer 2

Sorry, there it is, external .js doc.

Answer 3

javascript can be written in .js file you just have to place the file in the same folder of html and use <script src="abc.js"></script> in html
(if another location mention source)