10PRINT in p5.js

sketch1.js

// 10print.org
// Animated version of 10 print.

var x = 0;
var y = 0;

function setup() {
  createCanvas(640, 360);
  background(255);
}

function draw() {
  if (random(1) > 0.5) {
    line(x, y, x+20, y+20);
  } 
  else {
    line(x, y+20, x+20, y);
  }

  x += 20;
  if (x > width) {
    x = 0;
    y += 20;
  }

  if (y > height) {
    background(255);
    x = 0;
    y = 0;
  }
}

sketch2.js

// 10print.org
// Static all in a loop

function setup() {
  createCanvas(640, 360);
}

function draw() {
  background(255);
  for (var y = 0; y < height; y += 20) {
    for (var x = 0; x < width; x += 20) {
      if (random(1) > 0.5) {
        line(x, y, x + 20, y + 20);
      } else {
        line(x, y + 20, x + 20, y);
      }
    }
  }
  noLoop();
}

sketch3.js

// 10print.org
// Ported from the book

var w = 16;
var h = 16;
var index = 0;

function setup() {
  createCanvas(640, 384);
  background('#0000ff');
  strokeWeight(3);
  stroke(224);
}

function draw() {
  var x1 = w*index;
  var x2 = x1 + w;
  var y1 = h*23;
  var y2 = h*24;
  if (random(2) < 1) {
    line(x2, y1, x1, y2);
  } 
  else {
    line(x1, y1, x2, y2);
  }
  
  index++;
  if (index == width/w) {
    var p = get(0, h, width, h*23);
    background('#0000ff');
    set(0, 0, p);
    index = 0;
  }
}

Hello Dan,
In sketch3.js, does get() means a screenshot of an area?
and set() means paste that area h height upper?