W3School TIY Editor

<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1.0"/>
<style>
canvas {
    border:1px solid #d3d3d3;
    background-color: #f1f1f1;
}
</style>
</head>

var redGamePiece, blueGamePiece, yellowGamePiece;

function startGame() {
    redGamePiece = new component(75, 75, "red", 10, 10);
    yellowGamePiece = new component(75, 75, "yellow", 50, 60);    
    blueGamePiece = new component(75, 75, "blue", 10, 110);
    myGameArea.start();
}

function component(width, height, color, x, y) {
    this.width = width;
    this.height = height;
    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();
    redGamePiece.update();
    yellowGamePiece.update();        
    blueGamePiece.update();
}

</script>

<p>一个游戏区域上有三个组件。</p>

<p>请注意，组件的堆叠顺序取决于它们在 updateGameArea 函数中更新的顺序。蓝色游戏块最后更新，并将被放置在黄色游戏块之上，黄色游戏块将被放置在红色游戏块之上。</p>

</body>
</html>