Question

我是Javascript编程的新手，我正在借助视频构建一个简单的乒乓球游戏。我已经按照视频中的每条指令进行操作，但它似乎没有工作。一旦超过画布宽度， ballX 应该在中间重置，但如果 X 击中右边的拍子，则应该反转。

if (ballX < 0) {
  if (ballY > paddle1Y &&
    ballY < paddle1Y + paddleHeight) {
    ballXSpeed = -ballXSpeed;
  } else {
    ballReset();
  }
  if (ballX > canvas.width) {
    if (ballY > paddle2Y &&
      ballY < paddleHeight + paddle2Y) {
      ballXSpeed = -ballXSpeed;
    } else {
      ballReset();
    }
  }
}; //ends movement();

Answer 1

我认为您应该将if结构更正为：

// if ballX is less than 0, expected to use is paddle1
if (ballX < 0) {
  if (ballY > paddle1Y &&
    ballY < paddle1Y + paddleHeight) {
    ballXSpeed = -ballXSpeed;
  } else {
    ballReset();
  }
}
// else if ballX is in the other side of the table, expected to use is paddle2
else if (ballX > canvas.width) {
  if (ballY > paddle2Y &&
    ballY < paddleHeight + paddle2Y) {
    ballXSpeed = -ballXSpeed;
  } else {
    ballReset();
  }
}

你的}; 错位了。

Answer 2

已移动} - 看看是否有帮助

if (ballX < 0) {
  if (ballY > paddle1Y &&
    ballY < paddle1Y + paddleHeight) {
    ballXSpeed = -ballXSpeed;
  } else {
    ballReset();
  }
} // added
if (ballX > canvas.width) { // this probably should be an else if but it really doesn't matter
  if (ballY > paddle2Y &&
    ballY < paddleHeight + paddle2Y) {
    ballXSpeed = -ballXSpeed;
  } else {
    ballReset();
  }
  // a } removed from here
} //ends movement();

Answer 3

如果ballX小于0，那么它永远不会大于画布宽度，这很简单地使代码部分无用。逻辑根本没有意义。

Answer 4

我怀疑这可能是一些括号问题。

if (ballX < 0) {
  if ((ballY > paddle1Y) &&
    ((ballY < paddle1Y) + paddleHeight))) {
    ballXSpeed = -ballXSpeed;
  } else {
    ballReset();
  }
} // added
if (ballX > canvas.width) { // this probably should be an else if but it really doesn't matter
  if ((ballY > paddle2Y) &&
    ((ballY < paddleHeight) + paddle2Y))) {
    ballXSpeed = -ballXSpeed;
  } else {
    ballReset();
  }
  // a } removed from here
} //ends movement();

尽管遵循了严格的说明，但代

4 个答案: