<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Canvas Clock</title>
</head>
<body>
<div style="margin:100px 100px;">
<canvas id="clock" height="200" width="200"></canvas>
</div>
</body>
<script>
var obj = document.getElementById('clock');
var ctx = obj.getContext('2d');
var width = ctx.canvas.width;
var height = ctx.canvas.height;
var r = width / 2;
var rem = width / 200; //比例
//画圆
function drawBackground() {
ctx.save();
ctx.translate(r, r);
ctx.beginPath();
ctx.lineWidth = 10 * rem;
//以0，0为原点，r为半径，0为起始角，2*Math.PI为结束角，顺时针画圆
ctx.arc(0, 0, r - ctx.lineWidth / 2, 0, 2 * Math.PI, false);
ctx.stroke();
var hourNumber = [3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 1, 2];
ctx.font = 18 * rem + 'px Arial';
ctx.textAlign = 'center';
ctx.textBaseline = 'middle';
//画出1-12的数字
hourNumber.forEach(function (number, i) {
var rad = 2 * Math.PI / 12 * i;
var x = Math.cos(rad) * (r - 30 * rem);
var y = Math.sin(rad) * (r - 30 * rem);
ctx.fillText(number, x, y);
});
//画出秒针走动的60个点
for (var i = 0; i < 60; i++) {
var rad = 2 * Math.PI / 60 * i;
var x = Math.cos(rad) * (r - 18 * rem);
var y = Math.sin(rad) * (r - 18 * rem);
ctx.beginPath();
if (i % 5 === 0) {
ctx.fillStyle = '#000';
ctx.arc(x, y, 2 * rem, 0, 2, 2 * Math.PI, false);
} else {
ctx.fillStyle = '#ccc';
ctx.arc(x, y, 2 * rem, 0, 2, 2 * Math.PI, false);
}
ctx.fill();
}
}
//绘制时针
function drawHour(hour, minute) {
ctx.save();
ctx.beginPath();
var rad = 2 * Math.PI / 12 * hour;
var mrad = 2 * Math.PI / 12 / 60 * minute;
ctx.rotate(rad + mrad);
ctx.lineWidth = 6;
ctx.lineCap = 'round';
ctx.moveTo(0, 10 * rem);
ctx.lineTo(0, -r / 2);
ctx.stroke();
ctx.restore();
}
//绘制分针
function drawMinute(minute) {
ctx.save();
ctx.beginPath();
var rad = 2 * Math.PI / 60 * minute;
ctx.rotate(rad);
ctx.lineWidth = 3 * rem;
ctx.lineCap = 'round';
ctx.moveTo(0, 10);
ctx.lineTo(0, -r + 30 * rem);
ctx.stroke();
ctx.restore();
}
//绘制秒针
function drawSecond(second) {
ctx.save();
ctx.beginPath();
ctx.fillStyle = '#c14443';
var rad = 2 * Math.PI / 60 * second;
ctx.rotate(rad);
ctx.moveTo(-2, 20 * rem);
ctx.lineTo(2, 20 * rem);
ctx.lineTo(1, -r + 18 * rem);
ctx.lineTo(-1, -r + 18 * rem);
ctx.fill();
ctx.restore();
}
//画时钟上的中心白色原点
function drawDot() {
ctx.beginPath();
ctx.fillStyle = '#fff';
ctx.arc(0, 0, 3 * rem, 0, 2 * Math.PI, false);
ctx.fill();
}
function draw() {
ctx.clearRect(0, 0, width, height);
var now = new Date();
var hour = now.getHours();
var minutes = now.getMinutes();
var seconds = now.getSeconds();
drawBackground();
drawHour(hour, minutes);
drawMinute(minutes);
drawSecond(seconds);
drawDot();
ctx.restore();
}
setInterval(draw, 1000); //每秒执行一次
</script>