Converting my Processing code to p5.js (ArrayList + others!)

[GoToLoop]

@Rod1C

class ParticleSystem {
  ArrayList<Particle> particles;
  PVector origin;
 
  ParticleSystem(PVector position) {
    origin = position.copy();
    particles = new ArrayList<Particle>();
  }
 
  function addParticle() {
    particles.add(new Particle(origin));
  }

  // ...
}

That’s not how we define classes’ constructor, methods & fields under JS syntax!
You should read the JS reference for it:

Classes - JavaScript | MDN

Also, there’s no ArrayList either. We use JS arrays instead:

Indexed collections - JavaScript | MDN

And while in Java we can generally omit the keyword this before accessing a class member, in JS it’s mandatory:

This Dot - Daniel Shiffman (Coding Train)

Now w/ all the info above, here’s a partial but proper JS conversion of your class ParticleSystem:

class ParticleSystem {
  constructor(position) {
    this.origin = position.copy();
    this.particles = [];
  }
 
  addParticle() {
    this.particles.push(new Particle(this.origin));
  }

  // ...
}