app3.js

let isDrawing  = false;
let lastX = 0;
let lastY = 0;


function draw (e) {
  if(!isDrawing) return ;
  console.log(e);
  ctx.beginPath();
  ctx.moveTo(lastX, lastY);
  ctx.lineTo(e.offsetX, e.offsetY);
  ctx.stroke();
}