Other ressources
This [online] book is the result of a simple question: What happens when we try to redefine the graphic design curriculum using a programming language as the tool for the designer?
A practical hands on book about beginner aesthetics and programming. It is based on processing not p5js, but the two are very similar so you will get started quickly.
A comprehensive guide to working with physics and concepts from Nature in Processing.
Since P5JS is based on javascript this is the place to go to get detailed understanding of the syntax. W3 Schools is an amazing guide to Javascript, HTML and CSS. Get all the basic concepts here. Use it as a place to look up information.
A workshop focusing on Bauhaus easthetics in processing. The course requires you to be a patreon.