<html>
<head>
</head>
<body>
<canvas id="myCanvas" width="400" height="300" style="border:#06F solid 2px;">您的浏览器还不支持啊</canvas>
<script type="text/javascript">
var c = document.getElementById("myCanvas");
var cxt = c.getContext("2d");
var slen = 60;
var mlen = 50;
var hlen = 40;
cxt.strokeRect(0, 0, c.width, c.height);
cxt.beginPath();
cxt.strokeStyle = "#00f";
cxt.fillStyle = "#00f";
cxt.arc(200, 150, 5, 0, 2*Math.PI, true);
cxt.fill();
cxt.closePath();
cxt.beginPath();
cxt.strokeStyle = "#00f";
cxt.arc(200, 150, 100, 0, 2*Math.PI, true);
cxt.stroke();
cxt.closePath();
cxt.beginPath();
cxt.translate(200, 150);
cxt.rotate(-Math.PI/2);
cxt.save();
for (var i=0; i<60; i++){
if (i % 5==0){
cxt.fillRect(80, 0, 20, 5);
cxt.fillText("" + (i/5==0 ? 12 : i/5), 70, 0);
}else{
cxt.fillRect(90, 0, 10, 2);
}
cxt.rotate(Math.PI/30);
}
cxt.closePath();
var ls = 0, lm = 0, lh = 0;
function Refresh(){
cxt.restore();
cxt.save();
cxt.rotate(ls * Math.PI / 30);
cxt.clearRect(5, -1, slen+1, 2+2);
cxt.restore(); cxt.save();
cxt.rotate(lm*Math.PI / 30);
cxt.clearRect(5, -1, mlen+1, 3+2);
cxt.restore(); cxt.save();
cxt.rotate(lh*Math.PI / 6);
cxt.clearRect(5, -3, hlen+1, 4+2);
var time = new Date();
var s = ls = time.getSeconds();
var m = lm = time.getMinutes();
var h = lh = time.getHours();
cxt.restore();
cxt.save();
cxt.rotate(s*Math.PI / 30);
cxt.fillRect(5, 0, mlen, 2);
cxt.restore(); cxt.save();
cxt.rotate(m*Math.PI / 30);
cxt.fillRect(5, 0, mlen, 3);
cxt.restore(); cxt.save();
cxt.rotate(h*Math.PI / 6);
cxt.fillRect(5, -2, hlen, 4);
}
var MyInterval = setInterval("Refresh();", 1000);
</script>
</body>
</html>
【此案例来自网络，模仿练习。涉及到的知识，html5 canvas 矩形圆形绘图，函数Math.PI】