javascript - 让方 block 移动？

Question

我试图让 div“ySpeed(1)”和“ySpeed(-1)”使 myGamePiece 上下移动，最终从左向右移动。我制作了两个名为 movePieceUp 和 movePieceDown 的函数。我不知道为什么这些功能不能正常工作。知道如何让 myGamePiece 正常工作吗？

function component(width, height, color, x, y, type) {
  this.type = type;
  if (type == "image") {
    this.image = new Image();
    this.image.src = color;
  }
  this.score = 0;
  this.width = width;
  this.height = height;
  this.speedX = 2;
  this.speedY = 2;
  this.x = x;
  this.y = y;
  this.gravity = 0;
  this.gravitySpeed = 0;
  this.color = color;
  this.update = function() {
    random = Math.floor((Math.random() * 200) + 1);
    random2 = Math.floor((Math.random() * 200) + 1);

    function getRandomColor() {
      var letters = '0123456789ABCDEF';
      var color = '#';
      for (var i = 0; i < 6; i++) {
        color += letters[Math.floor(Math.random() * 16)];
      }
      return color;
    }
    randcolor = getRandomColor();
    ctx = myGameArea.context;
    if (this.type == "image") {
      ctx.drawImage(this.image, this.x, this.y, this.width, this.height);
    } else {
      ctx.fillStyle = randcolor;
      ctx.fillRect(random, random2, 50, 50);
    }
    this.x = random;
    this.y = random2;
    this.width = 50;
    this.height = 50;
    this.color = randcolor;
  }

}


function component2(width, height, color, x, y, type) {
  this.type = type;
  if (type == "image") {
    this.image = new Image();
    this.image.src = color;
  }
  this.score = 0;
  this.width = width;
  this.height = height;
  this.speedX = 2;
  this.speedY = 2;
  this.x = x;
  this.y = y;
  this.gravity = 2;
  this.gravitySpeed = 0;
  this.update = function() {
    ctx = myGameArea.context;
    if (this.type == "image") {
      ctx.drawImage(this.image, this.x, this.y, this.width, this.height);
    } else {
      ctx.fillStyle = color;
      ctx.fillRect(this.x, this.y, this.width, this.height);
    }
  }
  this.newPos = function() {
    this.x = this.x + this.speedX;
    this.y = this.y + this.speedY;
    //removed hitting rock bottom because the background and other pieces will be off screen.

  }
  this.hitBottom = function() {
    var rockbottom = myGameArea.canvas.height - this.height;
    if (this.y > rockbottom) {
      this.y = rockbottom;
      this.gravitySpeed = 0;
      board = 1;
    }
  }
  this.crashWith = function(otherobj) {
    var myleft = this.x;
    var myright = this.x + (this.width);
    var mytop = this.y;
    var mybottom = this.y + (this.height);
    var otherleft = otherobj.x;
    var otherright = otherobj.x + (otherobj.width);
    var othertop = otherobj.y;
    var otherbottom = otherobj.y + (otherobj.height);
    var crash = true;
    if ((mybottom < othertop) || (mytop > otherbottom) || (myright < otherleft) || (myleft > otherright)) {
      crash = false;
    }
    return crash;
  }
}

function startGame() {
  random = Math.floor((Math.random() * 100) + 1);


  random2 = Math.floor((Math.random() * 100) + 1);


  square = new component(50, 50, "green", random, random2);
  myGamePiece = new component2(30, 40, "greenhorn.gif", 220, 120);
  enemyPiece2 = new component(50, 50, "Trump1.jpg", random, random2, );
  myGameArea.start();
  return square
}

var myGameArea = {
  canvas: document.createElement("canvas"),
  start: function() {

    this.canvas.width = 450;
    this.canvas.height = 270;
    this.context = this.canvas.getContext("2d");
    document.body.insertBefore(this.canvas, document.body.childNodes[0]);

    this.interval = setInterval(updateGameArea, 1000);
  },
  clear: function() {
    this.context.clearRect(0, 0, this.canvas.width, this.canvas.height);
  }
}



function updateGameArea() {

  myGameArea.clear();
  square.update();
  myGamePiece.update();
  enemyPiece2.update();

}

function movePieceUp() {
  myGamePiece.ySpeed(1);
  myGamePiece.speedY = 2;
}

function movePieceDown() {
  myGamePiece.ySpeed(-1);
  myGamePiece.speedX = 2;
}


document.getElementById("start").addEventListener('click', startGame);
document.getElementById("ySpeed(1)").addEventListener('click', movePieceUp);
document.getElementById("ySpeed(-1)").addEventListener('click', movePieceDown);

<p> Click Start Game to play </p>
<div id="start">Start Game</div>
<div id="hi">Hi</div>


<div id="ySpeed(1)">UP</div>
</p>
<div id="ySpeed(-1)">DOWN</div>

Answer 1

您需要在一个位置声明 myGamePiece 变量，以便使用它的函数可以访问它。通过在函数调用外部和之前声明它使其成为“全局”变量，或者将变量作为参数传递给适当的函数。