Programming Design Systems is a free digital book that teaches a practical introduction to the new foundations of graphic design...
The book is written for readers with an introductory knowledge of programming in JavaScript, which means that little time will be devoted to explaining concepts like variables, functions, and loops. For this audience, I highly recommend Daniel Shiffman's Coding Rainbow YouTube channel, where Dan does a much better job explaining these concepts than I ever could. These videos will also introduce the basic concepts of programming in P5.