How to translate this Processing code to p5.js?

Question

A few years ago, I programmed this with Processing:

 import processing.pdf.*; drawing w; void setup() { size(1080, 720); beginRecord(PDF, "drawing.pdf"); w = new drawing(); background(0); } void draw() { w.step(); w.render(); } class drawing { float x, y; float tx, ty; float prevX, prevY; drawing() { tx = 0; ty = 90000; x = map(noise(tx), 0, 0.2, 0, width); y = map(noise(ty), 0, 0.2, 0, height); } void render() { stroke(255); line(prevX, prevY, x, y); } void step() { prevX = x; prevY = y; x = map(noise(tx), 0, 1, 0, width); y = map(noise(ty), 0, 1, 0, height); tx += 0.01; ty += 0.01; } } void keyPressed() { if (key == 'a') { endRecord(); exit(); } }

Now I would like to have it as p5.js code. I thought it could work this way:

 drawing w; function setup() { createCanvas(720, 400); w = new drawing(); background(0); } function draw() { w.step(); w.render(); } class drawing { float x, y; float tx, ty; float prevX, prevY; drawing() { tx = 0; ty = 90000; x = map(noise(tx), 0, 0.2, 0, width); y = map(noise(ty), 0, 0.2, 0, height); } function render() { stroke(255); line(prevX, prevY, x, y); } function step() { prevX = x; prevY = y; x = map(noise(tx), 0, 1, 0, width); y = map(noise(ty), 0, 1, 0, height); tx += 0.01; ty += 0.01; } }

 <script src="https://cdn.jsdelivr.net/npm/p5@1.4.1/lib/p5.js"></script>

Unfortunately, it doesn't work. Has anyone an idea how to fix that?

Answer 1

A lot of your java code hasn't been well translated to javascript.

I changed the following:

1. Java declares variables with the keyword of the type of the variable being declared: for example, float x . In JS, however you use let such as let x .
2. Class definitions are completely different. Look at the documentation for more information.

 class Drawing { constructor() { this.tx = 0; this.ty = 90000; this.x = map(noise(this.tx), 0, 0.2, 0, width); this.y = map(noise(this.ty), 0, 0.2, 0, height); } render() { stroke(255); line(this.prevX, this.prevY, this.x, this.y); } step() { this.prevX = this.x; this.prevY = this.y; this.x = map(noise(this.tx), 0, 1, 0, width); this.y = map(noise(this.ty), 0, 1, 0, height); this.tx += 0.01; this.ty += 0.01; } } let w; function setup() { createCanvas(720, 400); w = new Drawing(); background(0); } function draw() { w.step(); w.render(); }

 <script src="https://cdn.jsdelivr.net/npm/p5@1.4.1/lib/p5.js"></script>

Answer 2

Here it is, you need to use constructor() to instantiate a new Object from Drawing, Also don't forget this keyword to access variables.

You can see it working here as well:

https://editor.p5js.org/ghaithalzein05/sketches/veGh2JAYC

let w;

function setup() {
  createCanvas(400, 400);
  background(0);
  w = new Drawing();
}

function draw() {
  w.step();
  w.render();
}

class Drawing {
  
  constructor() {
    this.nextX = 0;
    this.nextY = 90000;
    this.x = map(noise(this.nextX), 0, 0.2, 0, width);
    this.y = map(noise(this.nextY), 0, 0.2, 0, height);
    this.px = 0;
    this.py = 0;
  }

   render() {
    stroke(255);
    line(this.px, this.py, this.x, this.y);
  }

   step() {
    this.px = this.x;
    this.py = this.y;
    this.x = map(noise(this.nextX), 0, 1, 0, width);
    this.y = map(noise(this.nextY), 0, 1, 0, height);
    this.nextX += 0.01;
    this.nextY += 0.01;
  }
}