5. Documentation for Three.js functions

The official Three.js website proposes a set of reference documentation from which you may find more information.
You may notably find

Documentation - The official documentation for all Three.js classes.
Examples A set of examples with source code
Source code The updated source code of the library and the examples.

As always, you may find a lot of resources on various internet website and forums. Keep, however, in mind that most of the up-to-date documentation you may need is usually available on the official website, and it is a good habit to check first the reference documentation .