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pong-solution.html
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<!DOCTYPE html>
<html>
<head>
<title>JS Pong</title>
<meta charset="UTF-8" />
<style>
html,
body {
height: 100%;
margin: 0;
}
body {
background: black;
display: flex;
align-items: center;
justify-content: center;
}
#game {
width: 100%;
height: 100%;
}
</style>
</head>
<body>
<canvas width="100" height="100" id="game"></canvas>
<script type="text/javascript">
const canvas = {
element: document.getElementById('game'),
context: null,
height: window.innerHeight,
width: window.innerWidth,
};
const config = {
gridSize: 15,
paddleSpeed: 6,
ballSpeed: 5,
};
config.paddleHeight = config.gridSize * 5; // 80
config.maxPaddleY =
canvas.height - config.gridSize - config.paddleHeight;
config.minPaddleY = config.gridSize;
const objects = {
leftPaddle: {
x: config.gridSize * 2,
y: canvas.height / 2 - config.paddleHeight / 2,
width: config.gridSize,
height: config.paddleHeight,
dy: 0,
},
rightPaddle: {
x: canvas.width - config.gridSize * 3,
y: canvas.height / 2 - config.paddleHeight / 2,
width: config.gridSize,
height: config.paddleHeight,
dy: 0,
},
ball: {
x: canvas.width / 2,
y: canvas.height / 2,
width: config.gridSize,
height: config.gridSize,
resetting: false,
dx: config.ballSpeed,
dy: -1 * config.ballSpeed,
},
};
const game = {
config: config,
canvas: canvas,
objects: objects,
collision: (obj1, obj2) => {
return (
obj1.x < obj2.x + obj2.width &&
obj1.x + obj1.width > obj2.x &&
obj1.y < obj2.y + obj2.height &&
obj1.y + obj1.height > obj2.y
);
// https://developer.mozilla.org/en-US/docs/Games/Techniques/2D_collision_detection
},
keyEvents: (_) => {
document.addEventListener('keydown', (e) => {
if (e.which === 38) {
objects.rightPaddle.dy = -1 * config.paddleSpeed;
} else if (e.which === 40) {
objects.rightPaddle.dy = config.paddleSpeed;
}
if (e.which === 87) {
objects.leftPaddle.dy = -1 * config.paddleSpeed;
} else if (e.which === 83) {
objects.leftPaddle.dy = config.paddleSpeed;
}
});
document.addEventListener('keyup', (e) => {
if (e.which === 38 || e.which === 40) {
objects.rightPaddle.dy = 0;
}
if (e.which === 83 || e.which === 87) {
objects.leftPaddle.dy = 0;
}
});
},
loop: (_) => {
canvas.context.clearRect(0, 0, canvas.width, canvas.height);
// move paddles by their velocity
objects.leftPaddle.y += objects.leftPaddle.dy;
objects.rightPaddle.y += objects.rightPaddle.dy;
// prevent paddles from going through walls
if (objects.leftPaddle.y < config.minPaddleY) {
objects.leftPaddle.y = config.minPaddleY;
} else if (objects.leftPaddle.y > config.maxPaddleY) {
objects.leftPaddle.y = config.maxPaddleY;
}
if (objects.rightPaddle.y < config.minPaddleY) {
objects.rightPaddle.y = config.minPaddleY;
} else if (objects.rightPaddle.y > config.maxPaddleY) {
objects.rightPaddle.y = config.maxPaddleY;
}
// draw paddles
canvas.context.fillStyle = 'white';
canvas.context.fillRect(
objects.leftPaddle.x,
objects.leftPaddle.y,
objects.leftPaddle.width,
objects.leftPaddle.height
);
canvas.context.fillRect(
objects.rightPaddle.x,
objects.rightPaddle.y,
objects.rightPaddle.width,
objects.rightPaddle.height
);
// move ball by its velocity
objects.ball.x += objects.ball.dx;
objects.ball.y += objects.ball.dy;
// prevent ball from going through walls by changing its velocity
if (objects.ball.y < config.gridSize) {
objects.ball.y = config.gridSize;
objects.ball.dy *= -1;
} else if (
objects.ball.y + config.gridSize >
canvas.height - config.gridSize
) {
objects.ball.y = canvas.height - config.gridSize * 2;
objects.ball.dy *= -1;
}
// reset ball if it goes past paddle (but only if we haven't already done so)
if (
(objects.ball.x < 0 || objects.ball.x > canvas.width) &&
!objects.ball.resetting
) {
objects.ball.resetting = true;
// give some time for the player to recover before launching the ball again
setTimeout(() => {
objects.ball.resetting = false;
objects.ball.x = canvas.width / 2;
objects.ball.y = canvas.height / 2;
}, 400);
}
// check to see if ball collides with paddle. if they do change x velocity
if (game.collision(objects.ball, objects.leftPaddle)) {
objects.ball.dx *= -1;
// move ball next to the paddle otherwise the collision will happen again
// in the next frame
objects.ball.x =
objects.leftPaddle.x + objects.leftPaddle.width;
} else if (
game.collision(objects.ball, objects.rightPaddle)
) {
objects.ball.dx *= -1;
// move ball next to the paddle otherwise the collision will happen again
// in the next frame
objects.ball.x =
objects.rightPaddle.x - objects.ball.width;
}
// draw ball
canvas.context.fillRect(
objects.ball.x,
objects.ball.y,
objects.ball.width,
objects.ball.height
);
// draw walls
canvas.context.fillStyle = 'lightgrey';
canvas.context.fillRect(
0,
0,
canvas.width,
config.gridSize
);
canvas.context.fillRect(
0,
canvas.height - config.gridSize,
canvas.width,
canvas.height
);
// draw dotted line down the middle
for (
let i = config.gridSize;
i < canvas.height - config.gridSize;
i += config.gridSize * 2
) {
canvas.context.fillRect(
canvas.width / 2 - config.gridSize / 2,
i,
config.gridSize,
config.gridSize
);
}
window.requestAnimationFrame(game.loop);
},
start: (_) => {
window.addEventListener('load', (_) => {
canvas.element.width = `${canvas.width}`;
canvas.element.height = `${canvas.height}`;
canvas.context = canvas.element.getContext('2d');
window.requestAnimationFrame(game.loop);
game.keyEvents();
});
},
};
game.start();
</script>
</body>
</html>