Seems like the p5.js online reference (https://p5js.org/reference/) is currently broken, with console errors:
https://p5js.org/assets/js/p5.min.js 404 (Not Found)
https://p5js.org/assets/js/p5.dom.min.js 404 (Not Found)
https://p5js.org/assets/js/p5.sound.min.js 404 (Not Found)
Can anyone confirm?