我目前正在对pong游戏进行编码。到目前为止，我已经写了这么多代码(如下(，但当我运行它时，除了画布的白色轮廓边框外，什么都没有出现。我尽力了，但失败了。请帮忙。
<!DOCTYPE html />
<html>
<head>
< title>Pong</title>
</head>
<body style="background-color:black;">
<center><canvas id="canvas" width="3000" height ="1500" style="border:2px solid #ffffff">
</canvas></center>
<script>
let cvs = document.getElementById('canvas')
let ctx = cvs.getContext('2d');
var GameHeight= 1500;
var GameWidth=3000;
let lastTime = 0;
class PaddleA {
constructor (gameHeight, gameWidth){
this.height = 365;
this.width = 30;
this.position = {x:30, y:(gameHeight/2)-(height/2)};
this.speed = 0;
this.maxSpeed = 10;
}
moveUp() {
this.speed = this.maxSpeed;
}
moveDown() {
this.speed = -this.maxSpeed;
}
stop () {
this.speed = 0;
}
draw (ctx){
ctx.fillStyle = '#fff';
ctx.fillRect(this.position.x, this.position.y, this.width, this.height);
}
update (deltaTime) {
if (!deltaTime) return;
this.position.y = this.speed;
//Preventing it to go off screen
if (this.position.y < 0) this.position.y =0;
if (this.position.y > gameHeight) this.position.y=0;
}
}
class PaddleB {
constructor (gameHeight, gameWidth){
this.height = 365;
this.width = 30;
this.position = {x:gameWidth - width - width, y:(gameHeight/2)-(height/2)};
this.speed = 0;
this.maxSpeed = 10;
}
moveUp() {
this.speed = this.maxSpeed;
}
moveDown() {
this.speed = -this.maxSpeed;
}
stop () {
this.speed = 0;
}
draw (ctx){
ctx.fillStyle = '#fff';
ctx.fillRect(this.position.x, this.position.y, this.width, this.height);
}
update (deltaTime) {
if (!deltaTime) return;
this.position.y = this.speed;
//Preventing it to go off screen
if (this.position.y < 0) this.position.y =0;
if (this.position.y > gameHeight) this.position.y=0;
}
}
//To do later
class Ball {
constructor (gameHeight, gameWidth) {
this.size = 100;
this.speed = 0;
this.maxSpeed = 10;
this.position = {x:gameWidth/2 - (ballSize/2), y:gameHeight/2 - (ballSize/2)};
}
draw (ctx) {
ctx.fillStyle = '#fff'
ctx.fillRect(this.position.x, this.position.y, this.size, this.size)
}
}
class inputHanlder {
constructor (paddleA) {
document.addEventListener('keydown', (event) => {
switch (event.keyCode) {
case 38:
paddleA.moveUp();
break
case 40:
paddleB.moveDown();
break
}
});
}
}
let paddleA = new PaddleA(GameHeight, GameWidth);
let paddleB = new PaddleB(GameHeight, GameWidth);
let ball = new Ball(GameHeight, GameWidth);
new inputHandler;
function gameLoop(timestamp) {
let deltaTime = timestamp - lastTime;
lastTime = tiemstamp;
ctx.clearRect (0, 0, gameWidth, gameHeight);
paddleA.update(deltaTime);
paddleA.draw(ctx);
paddleB.update(deltaTime);
paddleB.draw(ctx);
ball.update(deltaTime);
ball.draw(ctx);
requestAnimationFrame(gameLoop);
}
</script>
</body>
</hmtl>
还要注意，由于我上面提到的原因，这个代码是不完整的。还请给我推荐一个好地方，在那里我可以学习JavaScript游戏开发
<!DOCTYPE html>
<html>
<head>
<title></title>
<style>
html, body {
height: 100%;
margin: 0;
}
body {
background: black;
display: flex;
align-items: center;
justify-content: center;
}
</style>
</head>
<body>
<canvas width="750" height="585" id="game"></canvas>
<script>
const canvas = document.getElementById('game');
const context = canvas.getContext('2d');
const grid = 15;
const paddleHeight = grid * 5; // 80
const maxPaddleY = canvas.height - grid - paddleHeight;
var paddleSpeed = 6;
var ballSpeed = 5;
const leftPaddle = {
// start in the middle of the game on the left side
x: grid * 2,
y: canvas.height / 2 - paddleHeight / 2,
width: grid,
height: paddleHeight,
// paddle velocity
dy: 0
};
const rightPaddle = {
// start in the middle of the game on the right side
x: canvas.width - grid * 3,
y: canvas.height / 2 - paddleHeight / 2,
width: grid,
height: paddleHeight,
// paddle velocity
dy: 0
};
const ball = {
// start in the middle of the game
x: canvas.width / 2,
y: canvas.height / 2,
width: grid,
height: grid,
// keep track of when need to reset the ball position
resetting: false,
// ball velocity (start going to the top-right corner)
dx: ballSpeed,
dy: -ballSpeed
};
// check for collision between two objects using axis-aligned bounding box (AABB)
// @see https://developer.mozilla.org/en-US/docs/Games/Techniques/2D_collision_detection
function collides(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;
}
// game loop
function loop() {
requestAnimationFrame(loop);
context.clearRect(0,0,canvas.width,canvas.height);
// move paddles by their velocity
leftPaddle.y += leftPaddle.dy;
rightPaddle.y += rightPaddle.dy;
// prevent paddles from going through walls
if (leftPaddle.y < grid) {
leftPaddle.y = grid;
}
else if (leftPaddle.y > maxPaddleY) {
leftPaddle.y = maxPaddleY;
}
if (rightPaddle.y < grid) {
rightPaddle.y = grid;
}
else if (rightPaddle.y > maxPaddleY) {
rightPaddle.y = maxPaddleY;
}
// draw paddles
context.fillStyle = 'white';
context.fillRect(leftPaddle.x, leftPaddle.y, leftPaddle.width, leftPaddle.height);
context.fillRect(rightPaddle.x, rightPaddle.y, rightPaddle.width, rightPaddle.height);
// move ball by its velocity
ball.x += ball.dx;
ball.y += ball.dy;
// prevent ball from going through walls by changing its velocity
if (ball.y < grid) {
ball.y = grid;
ball.dy *= -1;
}
else if (ball.y + grid > canvas.height - grid) {
ball.y = canvas.height - grid * 2;
ball.dy *= -1;
}
// reset ball if it goes past paddle (but only if we haven't already done so)
if ( (ball.x < 0 || ball.x > canvas.width) && !ball.resetting) {
ball.resetting = true;
// give some time for the player to recover before launching the ball again
setTimeout(() => {
ball.resetting = false;
ball.x = canvas.width / 2;
ball.y = canvas.height / 2;
}, 400);
}
// check to see if ball collides with paddle. if they do change x velocity
if (collides(ball, leftPaddle)) {
ball.dx *= -1;
// move ball next to the paddle otherwise the collision will happen again
// in the next frame
ball.x = leftPaddle.x + leftPaddle.width;
}
else if (collides(ball, rightPaddle)) {
ball.dx *= -1;
// move ball next to the paddle otherwise the collision will happen again
// in the next frame
ball.x = rightPaddle.x - ball.width;
}
// draw ball
context.fillRect(ball.x, ball.y, ball.width, ball.height);
// draw walls
context.fillStyle = 'lightgrey';
context.fillRect(0, 0, canvas.width, grid);
context.fillRect(0, canvas.height - grid, canvas.width, canvas.height);
// draw dotted line down the middle
for (let i = grid; i < canvas.height - grid; i += grid * 2) {
context.fillRect(canvas.width / 2 - grid / 2, i, grid, grid);
}
}
// listen to keyboard events to move the paddles
document.addEventListener('keydown', function(e) {
// up arrow key
if (e.which === 38) {
rightPaddle.dy = -paddleSpeed;
}
// down arrow key
else if (e.which === 40) {
rightPaddle.dy = paddleSpeed;
}
// w key
if (e.which === 87) {
leftPaddle.dy = -paddleSpeed;
}
// a key
else if (e.which === 83) {
leftPaddle.dy = paddleSpeed;
}
});
// listen to keyboard events to stop the paddle if key is released
document.addEventListener('keyup', function(e) {
if (e.which === 38 || e.which === 40) {
rightPaddle.dy = 0;
}
if (e.which === 83 || e.which === 87) {
leftPaddle.dy = 0;
}
});
// start the game
requestAnimationFrame(loop);
</script>
</body>
</html>