Grid pack

gridPack.js

let gridFlag = []; //array of underlying grid flags (true==filled)
let shapes = []; //array of shape objects
let dx,dy; // grid spacing

function setup() {
  createCanvas(1000,1000);
  iNum = 20;
  jNum = 20;
  dx = width/iNum;;
  dy = height/jNum;
  for (let i=0; i<iNum*jNum; i++){
    gridFlag.push(false);
  }
  background(0)
  // drawGrid
  noFill();
  stroke(100)
  for (let i=0; i<iNum; i++){
    for (let j=0; j<jNum; j++){
      rect(i*dx,j*dy,dx,dy)
    }
  }
}


function draw() {
  
  let placedFlag = false;
  let count = 0;
  let maxCount = 1000000
  while (!placedFlag && count<maxCount){
    let randi = ~~random(iNum);
    let randj = ~~random(jNum);
    let randh = random([1,2,4,8]);
    let randw = randh*2;
    if (checkGrid(randi,randj,randw,randh)){
      shapes.push(new Shape(randi,randj,randw,randh));
      placedFlag = true;  
    } 
    count++;
    if (count==maxCount) noLoop()
  }

  // draw the shape that was just placed
  shapes[shapes.length-1].draw();

}

function checkGrid(iStart,jStart,w,h){
  for (let i=iStart; i<iStart+w; i++){
    for (let j=jStart;j<jStart+h;j++){
      if (i<0 || i>=iNum || j<0 || j>=jNum) return false;
      let gridIndex = j*iNum+i;
      if (gridFlag[gridIndex]) return false;
    }
  }
  // if you're here, all spots on grid were clear
  // go back through and save all those spots as filled (true)
  for (let i=iStart;i<iStart+w;i++){
    for (let j=jStart;j<jStart+h;j++){
      let gridIndex = j*iNum+i;
      gridFlag[gridIndex] = true;
    }
  }
  return true;
}

class Shape {
  constructor(i,j,width,height) {
    this.i = i;
    this.j = j;
    this.width = width;
    this.height = height;
  }
  draw(){
    fill(255)
    rect(this.i*dx+dx/4,this.j*dy+dx/4,this.width*dx-dx/2,this.height*dy-dy/2)
  }
}