<html>
<head>
<style>
canvas {border:1px solid black;}
</style>
</head>
<body>
<button onclick="myFunction()">尝试一下</button>
<p>点击按钮创建 CANVAS 元素，绘制一个红色矩形。</p>
<script>
function myFunction()
{
var x = document.createElement("CANVAS");
var ctx=x.getContext("2d");
ctx.fillStyle="#FF0000";
ctx.fillRect(20,20,150,100);
document.body.appendChild(x);
}
</script>
</body>
</html>