W3Schools 代码 - Tryit - v3.6

<!DOCTYPE html>
<html>
<head><meta http-equiv="content-security-policy" content="script-src 'none'">
<meta name="viewport" content="width=device-width, initial-scale=1.0"/>
<style>
canvas {
    border:1px solid #d3d3d3;
    background-color: #f1f1f1;
}
</style>
</head>
<body onload="startGame()">
<script>

var myGamePiece;

function startGame() {
    myGamePiece = new component(30, 30, "red", 10, 120);
    myGameArea.start();
}

var myGameArea = {
    canvas : document.createElement("canvas"),
    start : function() {
        this.canvas.width = 480;
        this.canvas.height = 270;
        this.canvas.style.cursor = "none"; //hide the original cursor
        this.context = this.canvas.getContext("2d");
        document.body.insertBefore(this.canvas, document.body.childNodes[0]);
        this.interval = setInterval(updateGameArea, 20);
        window.addEventListener('mousemove', function (e) {
            myGameArea.x = e.pageX;
            myGameArea.y = e.pageY;
        })
    },
    clear : function(){
        this.context.clearRect(0, 0, this.canvas.width, this.canvas.height);
    }
}
function component(width, height, color, x, y) {
    this.width = width;
    this.height = height;
    this.speedX = 0;
    this.speedY = 0;
    this.x = x;
    this.y = y;
    this.update = function() {
        ctx = myGameArea.context;
        ctx.fillStyle = color;
        ctx.fillRect(this.x, this.y, this.width, this.height);
    }
}

function updateGameArea() {
    myGameArea.clear();
    if (myGameArea.x && myGameArea.y) {
        myGamePiece.x = myGameArea.x;
        myGamePiece.y = myGameArea.y;
    }
    myGamePiece.update();
}
</script>
<p>Перемістіть курсор всередину полотна, щоб перемістити червоний квадрат.</p>
</body>
</html>