试图让div在keydown上移动到屏幕上

Question

我正在尝试制作一个游戏，玩家必须在迷宫中导航鼠标才能找到奶酪块。我在让div移动我想要的方式时遇到了一些麻烦。问题是当你按下向下箭头键（我用来测试它的键）它不会像我想要的那样以10的增量继续下降。我试过循环，整个shebang但我无法弄清楚如何让它工作。

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

您可以使用Player对象并修改它的x和y属性。 还要创建一个K对象，将当前使用的键编号设置为布尔值。 比像requestAnimationFrame这样的循环内移动玩家：

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，只要按下按键（就像输入一样），就可以通过Npx步骤移动元素并重复：

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 2

你每次都将它设置为10，使用split来获得值：

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

Answer 3

即使其他答案使用parseInt，最好将变量保存在代码中

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">