Question

<!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>
<body>
<canvas id="GameArea"></canvas>
<script>

var myGamePiece;

 myGamePiece = new component(30, 30, "red", 10, 120);




function component(width, height, color, x, y) {
    console.log("component  called");
    this.width = width;
    this.height = height;
    this.x = x;
    this.y = y; 
   var  myGameArea=document.getElementById("startGame"); 
   console.log("myGameArea");  
    var ctx = myGameArea.getContext("2d");
    console.log("crossed");
    ctx.fillStyle = color;
    ctx.fillRect(this.x, this.y, this.width, this.height);
}

</script>

<p>We have added a component to our game, a red square!</p>

</body>
</html>

//无法解决我的错误在上面的代码中，我尝试在调用一些名为component的函数时创建一个矩形。它按上下文创建了一个矩形但我收到了错误

Answer 1

您的画布的ID为＆＃34; GameArea＆＃34;，但您正在尝试执行getElementById（＆＃34; startGame＆＃34;）。

Answer 2

您的canvas元素ID是“GameArea”，但您在代码中称为“startGame”。这就是它为空的原因

我收到的错误是无法读取属性＆＃39;获取上下文＆＃39;为null

2 个答案: