看效果（欢迎各位同学推荐更好的gif制作软件）
请看代码
1 <!DOCTYPE html> 2 <html lang="en"> 3 <head> 4 <meta charset="UTF-8"> 5 <title>Title</title> 6 <style> 7 body { 8 padding: 0; 9 margin: 0; 10 background-color: rgba(0, 0, 0, 1); 11 } 12 13 canvas { 14 background-color: rgba(255, 255, 255, 1); 15 display: block; 16 margin: 10px auto; 17 } 18 </style> 19 </head> 20 <body> 21 <canvas id="clock" width="600" height="600">当前浏览器不支持Canvas</canvas> 22 <script> 23 (function(){ 24 let canvas = document.querySelector("#clock"); 25 let ctx = canvas.getContext("2d"); 26 existRequestAnimationFrame(); 27 draw(ctx); 28 })(); 29 function existRequestAnimationFrame(){ 30 var vendors = ['webkit', 'moz']; 31 for (var i = 0; i < vendors.length && !window.requestAnimationFrame; ++i) { 32 var vp = vendors[i]; 33 window.requestAnimationFrame = window[vp+'RequestAnimationFrame']; 34 } 35 if(!window.requestAnimationFrame){ 36 var lastTime = 0; 37 window.requestAnimationFrame = function(callback){ 38 var now = new Date().getTime(); 39 var nextTime = Math.max(lastTime + 16, now);//浏览器渲染的间隔时间大约16ms 40 return window.setTimeout(function(){ 41 callback(lastTime = nextTime); 42 },nextTime - now); 43 }; 44 } 45 } 46 function draw(ctx){ 47 requestAnimationFrame(function step(){ 48 drawDial(ctx); //绘制表盘 49 drawAllHands(ctx); //绘制时分秒针 50 requestAnimationFrame(step); 51 }); 52 } 53 /*绘制时分秒针*/ 54 function drawAllHands(ctx){ 55 let time = new Date(); 56 let s = time.getSeconds(),m = time.getMinutes(),h = time.getHours(); 57 let pi = Math.PI; 58 let secondAngle = pi / 180 * 6 * s + time.getMilliseconds()*pi*6/1000/180; //计算出来s针的弧度 59 let minuteAngle = pi / 180 * 6 * m + secondAngle / 60; //计算出来分针的弧度 60 let hourAngle = pi / 180 * 30 * h + minuteAngle / 12; //计算出来时针的弧度 61 drawHand(hourAngle, 90, 6, "NavyBlue", ctx); //绘制时针 62 drawHand(minuteAngle, 146, 4, "black", ctx); //绘制分针 63 drawHand(secondAngle, 248, 2, "red", ctx); //绘制秒针 64 } 65 /* 绘制时针、或分针、或秒针 66 * 参数1：要绘制的针的角度 67 * 参数2：要绘制的针的长度 68 * 参数3：要绘制的针的宽度 69 * 参数4：要绘制的针的颜色 70 * 参数4：ctx 71 * */ 72 function drawHand(angle, len, width, color, ctx){ 73 ctx.save(); 74 ctx.translate(300, 300); //把坐标轴的远点平移到原来的中心 75 ctx.rotate(-Math.PI / 2 + angle); //旋转坐标轴。 x轴就是针的角度 76 ctx.beginPath(); 77 ctx.moveTo(-4, 0); 78 ctx.lineTo(len, 0); // 沿着x轴绘制针 79 ctx.lineWidth = width; 80 ctx.strokeStyle = color; 81 ctx.lineCap = "round"; 82 ctx.stroke(); 83 ctx.closePath(); 84 ctx.restore(); 85 } 86 /*绘制表盘*/ 87 function drawDial(ctx){ 88 let pi = Math.PI; 89 ctx.clearRect(0, 0, 600, 600); //清除所有内容 90 ctx.save(); 91 92 //设置canvas四边角弧度区域为背景色 93 ctx.translate(0, 0); 94 ctx.beginPath(); 95 ctx.fillStyle = 'rgba(0, 0, 0, 1)'; 96 ctx.fillRect(0,0,600,600); 97 ctx.fill(); 98 ctx.translate(300, 300); 99 ctx.beginPath(); 100 ctx.arc(0, 0, 300, 0, 2 * pi); //绘制圆周 101 ctx.fillStyle = 'rgb(255,255,255)'; 102 ctx.fill(); 103 ctx.stroke(); 104 ctx.closePath(); 105 //绘制数字 106 for (let i = 0; i < 12; i++){ 107 let deg = -pi / 2 + i * pi / 6 + pi / 180 * 30,//旋转的角度 108 text = (i+1)+'';//数值 109 ctx.save(); 110 ctx.beginPath(); 111 ctx.font = '27px Microsoft Yahei'; 112 ctx.fillStyle = 'rgb(0,0,0)'; 113 ctx.fillText(text, 250*Math.cos(deg) - 6, 250*Math.sin(deg) + 7); 114 ctx.restore(); 115 } 116 ctx.restore(); 117 } 118 </script> 119 </body> 120 </html>
转载请注明出处，谢谢~
参考资料
http://www.w3school.com.cn/tags/html_ref_canvas.asp
http://www.runoob.com/html/html5-canvas.html
https://blog.csdn.net/u012468376/article/details/73350998