HTML5画矩形

1、源码
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>HTML5画矩形</title>
<script>
    function draw(id)
	{
		var canvas = document.getElementById("canvas");
		if(canvas == null)
		{
			return false;	
		}
		
		var context = canvas.getContext("2d");
		context.fillStyle = "#FF00000";
		context.fillRect(0,0,500,600);
		for(var i=0;i<10;i++)
		{
			context.beginPath();
			context.arc(i*25,i*25,i*10,0,Math.PI*2,true);
			context.closePath();
			context.fillStyle = "#00FF00";
			context.fill();
		}
	}
</script>
</head>

<body onLoad="draw('canvas')">
   <canvas id="canvas" width="500px" height="600px"></canvas>
</body>
</html>
2、结果