JavaScript Canvas 绘制动态时钟详解

var canvas = document.getElementById('myCanvas');
var ctx = canvas.getContext('2d');
ctx.beginPath();
ctx.arc(X坐标, Y坐标, 半径, 0, 2 * Math.PI, false);
ctx.strokeStyle = 随便填颜色;
ctx.stroke();
ctx.closePath();

//计算圆上每个点的坐标
///[a]角度[i]刻度[ox]圆心X坐标[oy]圆心Y坐标[or]圆半径
function angle(a, i, ox, oy, or) {
    var hudu = (2 * Math.PI / 360) * a * i;//求出弧度
    var x = ox + Math.sin(hudu) * or;//计算出x轴坐标for正弦
    var y = oy - Math.cos(hudu) * or;//计算出y轴坐标for余弦
    return x + '_' + y;
}

//打上文字（仅小时）
for (var i = 0; i < 12; i++) {
    var textXY = angle(30, i + 1, ox, oy, or - 10);//小时刻度坐标
    ctx.fillText(i + 1, textXY.split('_')[0], textXY.split('_')[1]);
    ctx.textAlign = 'center';//水平居中
    ctx.textBaseline = 'middle';//垂直居中
}
 
//打上分秒钟刻度
for (var i = 0; i < 60; i++) {
    var oXY = angle(6, i + 1, ox, oy, or);//分、秒刻度坐标
    ctx.beginPath();
    ctx.arc(oXY.split('_')[0], oXY.split('_')[1], (i + 1) % 5 == 0 ? 2 : 1, 0, 2 * Math.PI);
    ctx.fillStyle = 'blue';
    ctx.fill();
    ctx.closePath();
}

<!DOCTYPE html>
<html>
<head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
    <title>小马的canvas练手作品-时钟</title>
    <meta charset="utf-8" />
</head>
<body>
    <canvas id="myCanvas" width="1000" height="1000">您的浏览器不支持此标签</canvas>
    <script type="text/javascript">
 
        setInterval('drawClock(150, 150, 100, 50, 70, 90,"pink","black","red","green")', 1000);
 
        //画钟表
        //[ox]圆心X坐标[oy]圆心Y坐标[or]钟表半径[hr]时针半径[mr]分针半径[sr]秒针半径[oc]钟表外环颜色[hc]时针颜色[mc]分针颜色[sc]秒针颜色
        function drawClock(ox, oy, or, hr, mr, sr, oc, hc, mc, sc) {
 
            //时钟底盘
            var canvas = document.getElementById('myCanvas');
            var ctx = canvas.getContext('2d');
            ctx.clearRect(ox - or, oy - or, or * 2, or * 2);//清空上一次绘制
            ctx.beginPath();
            ctx.arc(ox, oy, or, 0, 2 * Math.PI, false);
            ctx.strokeStyle = oc;
            ctx.stroke();
            ctx.closePath();
 
            //获取当前时间
            var NowTime = new Date();
            var h = NowTime.getHours();
            var m = NowTime.getMinutes();
            var s = NowTime.getSeconds();
            var y = NowTime.getFullYear();
            var mo = NowTime.getMonth() + 1;
            var d = NowTime.getDate();
            ctx.fillText(mo + '月' + d + '日', ox, oy - or / 2, 50);//显示月日
 
            //打上时间刻度
            for (var i = 0; i < 12; i++) {
                var textXY = angle(30, i + 1, ox, oy, or - 10);//小时刻度坐标
                ctx.fillText(i + 1, textXY.split('_')[0], textXY.split('_')[1]);
                ctx.textAlign = 'center';//水平居中
                ctx.textBaseline = 'middle';//垂直居中
            }
 
            //打上分钟刻度
            for (var i = 0; i < 60; i++) {
                var oXY = angle(6, i + 1, ox, oy, or);//分、秒刻度坐标
                ctx.beginPath();
                ctx.arc(oXY.split('_')[0], oXY.split('_')[1], (i + 1) % 5 == 0 ? 2 : 1, 0, 2 * Math.PI);
                ctx.fillStyle = 'blue';
                ctx.fill();
                ctx.closePath();
            }
 
            h = h + m / 60;//分钟影响时针偏移
 
            var hoursXY = angle(30, h > 12 ? h - 12 : h, ox, oy, hr);//时针终点XY坐标
            drawLine(ctx, hc, ox, oy, hoursXY.split('_')[0], hoursXY.split('_')[1]);
 
            m = m + s / 60;//秒钟影响分针偏移
 
            var minuteXY = angle(6, m, ox, oy, mr);//分针终点XY坐标
            drawLine(ctx, mc, ox, oy, minuteXY.split('_')[0], minuteXY.split('_')[1]);
 
            var secondXY = angle(6, s, ox, oy, sr);//秒针终点XY坐标
            drawLine(ctx, sc, ox, oy, secondXY.split('_')[0], secondXY.split('_')[1]);
 
        }
 
        //计算圆上每个点的坐标
        ///[a]角度[i]刻度[ox]圆心X坐标[oy]圆心Y坐标[or]圆半径
        function angle(a, i, ox, oy, or) {
            var hudu = (2 * Math.PI / 360) * a * i;//求出弧度
            var x = ox + Math.sin(hudu) * or;//计算出x轴坐标for正弦
            var y = oy - Math.cos(hudu) * or;//计算出y轴坐标for余弦
            return x + '_' + y;
        }
 
        //画线方法
        ///[ob]绘画对象[ox]圆心X坐标[oy]圆心Y坐标[px]目标X坐标[py]目标Y坐标
        function drawLine(ob, color, ox, oy, px, py) {
            ob.beginPath();
            ob.strokeStyle = color;
            ob.moveTo(ox, oy);
            ob.lineTo(px, py);
            ob.stroke();
            ob.closePath();
        }<br data-filtered="filtered">
    </script>
</body>
</html>