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I decided to make a Breakout game in JavaScript. Is there a way of making it cleaner? For instance, creating objects for the ball and the paddle.

<!DOCTYPE html>
<html>

<head>
  <meta charset="UTF-8">
  <title>Brick Game</title>

  <style type="text/css">
    body {
      background-color: black;
    }
    canvas {
      border: 1px solid green;
    }
  </style>

</head>

<body>


  <canvas id="game-canvas" height="600px" width="800px" </canvas>

    <script type="text/javascript">
      var canvas = document.getElementById("game-canvas");
       // Get a 2D context for the canvas.
      var ctx = canvas.getContext("2d");


      var ballR = 10;
      var x = canvas.width / 2;
      var y = canvas.height - 30;
      var dx = 3;
      var dy = -3;
      var pongH = 15;
      var pongW = 80;
      var pongX = (canvas.width - pongW) / 2;
      var rightKey = false;
      var leftKey = false;
      var brickRows = 3;
      var brickCol = 9;
      var brickW = 75;
      var brickH = 20;
      var brickPadding = 10;
      var brickOffsetTop = 30;
      var brickOffsetLeft = 30;

      var bricks = [];
      for (c = 0; c < brickCol; c++) {
        bricks[c] = [];
        for (r = 0; r < brickRows; r++) {
          bricks[c][r] = {
            x: 0,
            y: 0,
            status: 1
          };
        }
      }


       // function to draw the ball 
      function drawBall() {
        ctx.beginPath();
        ctx.arc(x, y, ballR, 0, Math.PI * 2);
        ctx.fillStyle = "red";
        ctx.fill();
        ctx.closePath();
      }

       // function draw the pong
      function drawPong() {
        ctx.beginPath();
        ctx.rect(pongX, canvas.height - pongH, pongW, pongH);
        ctx.fillStyle = "blue";
        ctx.fill();
        ctx.closePath();
      }

       // function draw the bricks
      function drawBricks() {
        for (c = 0; c < brickCol; c++) {
          for (r = 0; r < brickRows; r++) {
            if (bricks[c][r].status == 1) {
              var brickX = (c * (brickW + brickPadding)) + brickOffsetLeft;
              var brickY = (r * (brickH + brickPadding)) + brickOffsetTop;
              bricks[c][r].x = brickX;
              bricks[c][r].y = brickY;
              ctx.beginPath();
              ctx.rect(brickX, brickY, brickW, brickH);
              ctx.fillStyle = "green";
              ctx.fill();
              ctx.closePath();
            }
          }
        }
      }

      function collisionDetection() {
        for (c = 0; c < brickCol; c++) {
          for (r = 0; r < brickRows; r++) {
            var b = bricks[c][r];
            if (b.status == 1) {
              if (x > b.x && x < b.x + brickW && y > b.y && y < b.y + brickH) {
                dy = -dy;
                b.status = 0;
              }
            }
          }
        }
      }



      function draw() {
        ctx.clearRect(0, 0, canvas.width, canvas.height);
        drawBricks();
        drawBall();
        drawPong();
        collisionDetection();

        if (x + dx > canvas.width - ballR || x + dx < ballR) {
          dx = -dx;
        }

        if (y + dy < ballR) {
          dy = -dy;
        } else if (y + dy > canvas.height - ballR) {
          if (x > pongX && x < pongX + pongW) {
            dy = -dy;
          } else {
            // if the ball hits the bottom of canvas
            // reload the game

            document.location.reload();
          }
        }
        // when key is pressed 
        function keyDown(e) {
          if (e.keyCode == 39) {
            rightKey = true;
          } else if (e.keyCode == 37) {
            leftKey = true;
          }
        }

        // when key is not pressed
        function keyUp(e) {
          if (e.keyCode == 39) {
            rightKey = false;
          } else if (e.keyCode == 37) {
            leftKey = false;
          }
        }

        // Add an event listener to the keypress event.
        document.addEventListener("keydown", keyDown, false);
        document.addEventListener("keyup", keyUp, false);

        // move the pong right if the right key pressed
        if (rightKey && pongX < canvas.width - pongW) {
          pongX += 7;
        }
        // move the pong left if the left key pressed
        else if (leftKey && pongX > 0) {
          pongX -= 7;
        }

        x += dx;
        y += dy;
      }

      setInterval(draw, 10);
    </script>
</body>

</html>

| improve this question | |
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4
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First, great job. I loved seeing that the whole game had been created with so little code, and was so easy to understand.

While you could consider making this more object-oriented, I don't think it's necessary, so I did some rewrites in keeping with the simple procedural style of the original.

The biggest place for improvement is in naming your concepts. For example, this:

if (hitSideWall())
    dx = -dx;
if (hitTop() || hitPong())
    dy = -dy;
if (gameOver())
  document.location.reload();

is much clearer than:

if (y + dy < ballR) {
  dy = -dy;
} else if (y + dy > canvas.height - ballR) {
  if (x > pongX && x < pongX + pongW) {
    dy = -dy;
  } else {
    document.location.reload();
  }
}

You can apply this principle over and over, at all levels of your code. See the full rewrite for more examples.

Other notes:

  • Avoid nesting wherever possible, and avoid "if... else" statements.
  • The nested for loop for the bricks only needs to be done once. Use it once to create a flat array of bricks. Afterward, the nested structure is superfluous, since each brick object contains the info you need. Just loop through the flat array with forEach.
  • When initializing multiple variables, just use one var and commas.

Full rewrite: 

<!DOCTYPE html>
<html>

<head>
  <meta charset="UTF-8">
  <title>Brick Game</title>
  <style type="text/css">
    body { background-color: black; }
    canvas { border: 1px solid green; }
  </style>
</head>

<body>

  <canvas id="game-canvas" height="600px" width="800px" </canvas>

    <script type="text/javascript">
      var canvas = document.getElementById("game-canvas"),
          ctx = canvas.getContext("2d"),
          ballR = 10,
          x = canvas.width / 2,
          y = canvas.height - 30,
          dx = 3,
          dy = -3,
          pongH = 15,
          pongW = 80,
          pongX = (canvas.width - pongW) / 2,
          rightKey = false,
          leftKey = false,
          brickRows = 3,
          brickCol = 9,
          brickW = 75,
          brickH = 20,
          brickPadding = 10,
          brickOffsetTop = 30,
          brickOffsetLeft = 30;

      var bricks = [];
      for (c = 0; c < brickCol; c++) {
        for (r = 0; r < brickRows; r++) {
          bricks.push({
            x: (c * (brickW + brickPadding)) + brickOffsetLeft,
            y: (r * (brickH + brickPadding)) + brickOffsetTop,
            status: 1
          });
        }
      }


       // function to draw the ball 
      function drawBall() {
        ctx.beginPath();
        ctx.arc(x, y, ballR, 0, Math.PI * 2);
        ctx.fillStyle = "red";
        ctx.fill();
        ctx.closePath();
      }

       // function draw the pong
      function drawPong() {
        ctx.beginPath();
        ctx.rect(pongX, canvas.height - pongH, pongW, pongH);
        ctx.fillStyle = "blue";
        ctx.fill();
        ctx.closePath();
      }

       // function draw the bricks
      function drawBricks() {
        bricks.forEach(function(brick) {
          if (!brick.status) return;
          ctx.beginPath();
          ctx.rect(brick.x, brick.y, brickW, brickH);
          ctx.fillStyle = "green";
          ctx.fill();
          ctx.closePath();
        });
      }

      function collisionDetection() {
        bricks.forEach(function(b) {
          if (!b.status) return;

          var inBricksColumn = x > b.x && x < b.x + brickW,
              inBricksRow = y > b.y && y < b.y + brickH;

          if (inBricksColumn && inBricksRow) {
            dy = -dy;
            b.status = 0;
          }
        });
      }

      function draw() {
        ctx.clearRect(0, 0, canvas.width, canvas.height);
        drawBricks();
        drawBall();
        drawPong();
        collisionDetection();

        if (hitSideWall())
            dx = -dx;
        if (hitTop() || hitPong())
            dy = -dy;
        if (gameOver())
          document.location.reload();

        var RIGHT_ARROW = 39,
            LEFT_ARROW= 37;

        function hitPong() { return hitBottom() && ballOverPong() }
        function ballOverPong() { return x > pongX && x < pongX + pongW }
        function hitBottom() { return y + dy > canvas.height - ballR }
        function gameOver() { return hitBottom() && !ballOverPong() }
        function hitSideWall() { return x + dx > canvas.width - ballR || x + dx < ballR }
        function hitTop() { return y + dy < ballR }
        function xOutOfBounds() { return x + dx > canvas.width - ballR || x + dx < ballR }
        function rightPressed(e) { return e.keyCode == RIGHT_ARROW }
        function leftPressed(e) { return e.keyCode == LEFT_ARROW }

        function keyDown(e) {
          rightKey = rightPressed(e); 
          leftKey = leftPressed(e);
        }

        function keyUp(e) {
          rightKey = rightPressed(e) ? false : rightKey;
          leftKey = leftPressed(e) ? false : leftKey;
        }

        // Add an event listener to the keypress event.
        document.addEventListener("keydown", keyDown, false);
        document.addEventListener("keyup", keyUp, false);

        // move the pong right if the right key pressed
        var maxX = canvas.width - pongW,
            minX = 0,
            pongDelta = rightKey ? 7 : leftKey ? -7 : 0;

        pongX = pongX + pongDelta;
        pongX = Math.min(pongX, maxX);
        pongX = Math.max(pongX, minX);

        x += dx;
        y += dy;
      }

      setInterval(draw, 10);
    </script>
</body>

</html>
| improve this answer | |
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