bouncingBall.js

var canvas = document.getElementById("myCanvas");
var ctx = canvas.getContext("2d");

function drawRect(x, y) {
	ctx.fillStyle = "green";
	ctx.fillRect(x, y, 50, 50);
}
  
// box co-ordinates
var x = 0;
var y = 0;

// destroy?
var destroy = false;

function draw() {
	ctx.clearRect(0, 0, 500, 500); // clear canvas
	drawRect(x, y);

  if(destroy != true) {
    if (x <= 450) {
      x = x + 5;
    }
	}
  
  if (destroy == true) {
    x = x - 5;
  }
  
  if (x == 450) {
  	destroy = true;
  }
  
  if (x == 0) {
    destroy = false;
  }

  window.requestAnimationFrame(draw);
}
window.requestAnimationFrame(draw);