Canvas：https://developer.mozilla.org/en/Canvas_tutorial、http://www.w3.org/TR/2dcontext/
三角函数：http://zh.wikipedia.org/zh/%E4%B8%89%E8%A7%92%E5%87%BD%E6%95%B0
JavaScript：https://developer.mozilla.org/en/JavaScript、http://www.w3school.com.cn/js/index.asp
源代码
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
<title>超酷HTML5时钟(作者：http://www.cnblogs.com/jscode/)</title>
<style type="text/css">
.time {
text-align: center;
width:400px;
font-family: "Book Antiqua",Palatino,serif;
font-size: 40px;
font-weight: bold;
text-shadow: 1px 1px 3px #333;
position:absolute;
}
.time em {
background: white;
position: absolute;
top: 5px;
left: 130px;
height: 18px;
width: 140px;
opacity: 0.4;
}
</style>
<script type="text/javascript">
var canvas, context;
function DrawClock() {
canvas = document.getElementById("canvas");
context = canvas.getContext("2d");
setInterval("drawbackground()", 1000);
}
function drawbackground() {
var radius = Math.min(canvas.width / 2, canvas.height / 2) - 15;
var centerx = canvas.width / 2;
var centery = canvas.height / 2;
context.clearRect(0, 0, canvas.width, canvas.height);
context.save();
context.lineWidth = 15;
context.fillStyle = "#EFEFEF";
context.strokeStyle = "#000";
context.beginPath();
context.arc(centerx, centery, radius, 0, Math.PI * 2, 0);
context.fill();
context.stroke();
context.closePath();
context.restore();
for (var i = 0; i < 60; i++) {
context.save();
context.fillStyle = "#EFEFEF";
context.strokeStyle = "#000";
if (i % 5 == 0) {
context.lineWidth = 3;
}
context.beginPath();
context.moveTo(centerx, centery);
context.lineTo(centerx + (radius-6) * Math.cos(i * 6 * Math.PI / 180), centery - (radius-5) * Math.sin(i * 6 * Math.PI / 180));
context.fill();
context.stroke();
context.closePath();
context.restore();
}
context.moveTo(centerx, centery);
context.save();
context.fillStyle = "#EFEFEF";
context.strokeStyle = "#EFEFEF";
context.beginPath();
context.arc(centerx, centery, radius-15, 0, Math.PI * 2, 0);
context.fill();
context.stroke();
context.closePath();
context.restore();
var r = radius - 25;
context.font = "bold 20px 宋体";
Drawtext("1", centerx + (Math.cos(60 * Math.PI / 180) * r), centery - (Math.sin(60 * Math.PI / 180) * r));
Drawtext("2", centerx + (Math.cos(30 * Math.PI / 180) * r), centery - (Math.sin(30 * Math.PI / 180) * r));
Drawtext("3", centerx + (Math.cos(0 * Math.PI / 180) * r), centery - (Math.sin(0 * Math.PI / 180) * r));
Drawtext("4", centerx + (Math.cos(330 * Math.PI / 180) * r), centery - (Math.sin(330 * Math.PI / 180) * r));
Drawtext("5", centerx + (Math.cos(300 * Math.PI / 180) * r), centery - (Math.sin(300 * Math.PI / 180) * r));
Drawtext("6", centerx + (Math.cos(270 * Math.PI / 180) * r), centery - (Math.sin(270 * Math.PI / 180) * r));
Drawtext("7", centerx + (Math.cos(240 * Math.PI / 180) * r), centery - (Math.sin(240 * Math.PI / 180) * r));
Drawtext("8", centerx + (Math.cos(210 * Math.PI / 180) * r), centery - (Math.sin(210 * Math.PI / 180) * r));
Drawtext("9", centerx + (Math.cos(180 * Math.PI / 180) * r), centery - (Math.sin(180 * Math.PI / 180) * r));
Drawtext("10", centerx + (Math.cos(150 * Math.PI / 180) * r), centery - (Math.sin(150 * Math.PI / 180) * r));
Drawtext("11", centerx + (Math.cos(120 * Math.PI / 180) * r), centery - (Math.sin(120 * Math.PI / 180) * r));
Drawtext("12", centerx + (Math.cos(90 * Math.PI / 180) * r), centery - (Math.sin(90 * Math.PI / 180) * r));
context.save();
context.fillStyle="black";
context.beginPath();
context.arc(centerx,centery,10,0,Math.PI*2,0);
context.fill();
context.stroke();
context.closePath();
context.restore();
drawpoint(centerx, centery, radius);
}
function drawpoint(centerx, centery, radius) {
var date = new Date();
var h = date.getHours();
h = h < 13 ? h : h - 12;
var m = date.getMinutes();
var s = date.getSeconds();
var th = date.getHours() < 10 ? "0" + date.getHours() : date.getHours();
var tm = m < 10 ? "0" + m : m;
var ts = s < 10 ? "0" + s : s;
document.getElementById("currtime").innerHTML = th + ":" + tm + ":" + ts;
var hr = h * 30 * Math.PI / 180 + (m / 60) * 30 * Math.PI / 180 + 90 * Math.PI / 180;
var mr = m * 6 * Math.PI / 180 + s / 60 * 6 * Math.PI / 180 + 90 * Math.PI / 180;
var sr = s * 6 * Math.PI / 180 + 90 * Math.PI / 180;
context.save();
context.lineWidth = 5;
context.fillStyle = "darkgray";
context.strokeStyle = "black";
context.beginPath();
context.moveTo(centerx + 20 * Math.cos(hr), centery + 20 * Math.sin(hr));
context.lineTo(centerx - (radius - 120) * Math.cos(hr), centery - (radius - 120) * Math.sin(hr));
context.moveTo(centerx + 20 * Math.cos(mr), centery + 20 * Math.sin(mr));
context.lineTo(centerx - (radius - 80) * Math.cos(mr), centery - (radius - 80) * Math.sin(mr));
context.moveTo(centerx + 20 * Math.cos(sr), centery + 20 * Math.sin(sr));
context.lineTo(centerx - (radius - 50) * Math.cos(sr), centery - (radius - 50) * Math.sin(sr));
context.closePath();
context.fill();
context.stroke();
context.restore();
}
function Drawtext(text, x, y) {
context.save();
x -= (context.measureText(text).width / 2);
y += 9;
context.beginPath();
context.translate(x, y);
context.fillText(text, 0, 0);
context.restore();
}
window.onload = DrawClock;
</script>
</head>
<body>
<h1>超酷HTML5时钟(作者：http://www.cnblogs.com/jscode/)</h1>
<canvas id="canvas" width="400px" height="400px"></canvas>
<div class="time"><span id="currtime">00:00:00</span><em></em></div>
</body>
</html>
方法作用解释：
DrawClock 方法取得 Canvas 上下文
drawbackground 方法主要是画时钟的背景部分：边框、文字、刻度线
drawpoint 方法用来画时、分、秒线
Drawtext 方法是添加文字的
