尝试让 div 在按下按键时在屏幕上移动

Question

我正在尝试制作一款游戏，玩家必须通过鼠标在迷宫中导航才能找到奶酪块。我在让 div 移动到我想要的位置时遇到了一些麻烦。问题是当你按下向下箭头键（我用来测试它的键）时，它不会像我想要的那样以十为增量继续下降。我试过循环，整个 shebang，但我就是不知道如何让它工作。

document.onkeydown = function(key){
    if (key.keyCode == 38){
        console.log("up");
    } else if (key.keyCode == 39){
        console.log("right");
    } else if (key.keyCode == 37){
        console.log("left");
    } else if (key.keyCode == 40){
        mouse.style.top = 10 + "px";
    };
};

Answer 1

你每次都设置为10，先用split取值：

else if (key.keyCode == 40){
    mouse.style.top = parseInt(mouse.style.top.split("px")[0]) + 10 + "px";
}

Answer 2

您可以使用 Player 对象并修改它的 x 和 y 属性。
还创建一个 K 对象以将当前使用的 keys 数字设置为布尔值。
比在 requestAnimationFrame 这样的循环中移动播放器：

const Player = {
  el: document.getElementById('mouse'),
  x: 200,
  y: 100,
  speed: 2,
  move() {
    // If no collision with map or tiles... (TODO!)
    this.el.style.transform = `translate(${this.x}px, ${this.y}px)`;
  }
};
 
const K = {
  fn(ev) {
    ev.preventDefault();
    const k = ev.which;
    if (k >= 37 && k <= 40) K[k] = ev.type === "keydown"; // If is arrow
  }
};
  
const update = () => {
    // 1 / Math.sqrt(2) = 0.7071.. (Diagonal)
    let dist = K[38] && (K[37] || K[39]) || K[40] && (K[37] || K[39]) ? 0.707 : 1;
    dist *= Player.speed;
    if (K[37]) Player.x -= dist;
    if (K[38]) Player.y -= dist;
    if (K[39]) Player.x += dist;
    if (K[40]) Player.y += dist;
    Player.move();
}

document.addEventListener('keydown', K.fn);
document.addEventListener('keyup', K.fn);

(function engine() {
  update();
  window.requestAnimationFrame(engine);
}());

#mouse{
  position: absolute;
  left: 0;  top: 0;
  width: 20px;  height: 20px;
  background: #000;  border-radius: 50%;
}

Click here to focus, and use arrows
<div id="mouse"></div>

一个更简单的例子，它通过Npx步移动元素并重复，只要你按住键（就像打字一样) 将是：

const Player = {
  el: document.getElementById('mouse'),
  x: 0,
  y: 0,
  step: 10,
  move() {
    this.el.style.transform = `translate(${this.x}px, ${this.y}px)`;
  }
};

const keysHandler = (ev) => {
  const k = ev.which;
  if (k>=37 && k<=40) {
    ev.preventDefault();
    ({
      '37' () {Player.x -= Player.step},
      '38' () {Player.y -= Player.step},
      '39' () {Player.x += Player.step},
      '40' () {Player.y += Player.step},
    }[k]());
    Player.move();
  }
}

document.addEventListener('keydown', keysHandler);

#mouse{
  position: absolute;
  left: 0;  top: 0;
  width: 20px;  height: 20px;
  background: #000;  border-radius: 50%;
}

Click here to focus, and use arrows
<div id="mouse"></div>

Answer 3

即使使用了其他答案parseInt，最好将变量保留在代码中

var x = 0;
var y = 0;

document.onkeydown = function(key){
    if (key.keyCode == 38){
        y -= 10;
    } else if (key.keyCode == 39){
        x += 10;
    } else if (key.keyCode == 37){
        x -= 10;
    } else if (key.keyCode == 40){
        y += 10;
    };
    
    document.getElementById("block").style.left = x+"px";
    document.getElementById("block").style.top = y+"px";
};

#block
{
  top: 0;
  left: 0;
  position: absolute;
  width: 30px;
  height: 60px;
  background: teal;
}

<div id="block">

尝试让 div 在按下按键时在屏幕上移动

Trying to make div move on screen on keydown

javascript

css

html

webpage