zig Tryit Editor

<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1.0"/>
<style>
canvas {
    border:1px solid #d3d3d3;
    background-color: #f1f1f1;
}
</style>
</head>
<body onload="startGame()">
<script>
  var myGamePiece;
  function startGame() {
    myGamePiece = new component(30, 30, "red", 10, 120);
    myGameArea.start();
  }
  var myGameArea = {
    canvas: document.createElement("canvas"),
    start: function () {
      this.canvas.width = 480;
      this.canvas.height = 270;
      this.context = this.canvas.getContext("2d");
      document.body.insertBefore(this.canvas, document.body.childNodes[0]);
      this.interval = setInterval(updateGameArea, 20);
    },
    clear: function () {
      this.context.clearRect(0, 0, this.canvas.width, this.canvas.height);
    }
  }
  function component(width, height, color, x, y) {
    this.width = width;
    this.height = height;
    this.x = x;
    this.y = y;
    this.update = function () {
      ctx = myGameArea.context;
      ctx.fillStyle = color;
      ctx.fillRect(this.x, this.y, this.width, this.height);
    }
  }
  function updateGameArea() {
    //myGameArea.clear();
    myGamePiece.x += 1;
    myGamePiece.update();
  }
</script>
<p>If we do not clear the game area at every update, a trail of all earlier movements will be shown.</p>
</body>

</html>