<canvas> 标签定义图形，比如图表和其他图像，您必须使用脚本来绘制图形。
接下来我们将跟大家分享如何在画布上（Canvas）画一个时钟。
先看下效果图：
源码
HTML 代码
<!DOCTYPE html><html> <head> <meta charset="utf-8" /> <title>HTML5 时钟</title> <script src="/images/2021/07/13/07/2021071307454112503931.js"></script> <style> .clocks { height: 500px; margin: 25px auto; position: relative; width: 500px; } </style> </head> <body> <header> <h2>HTML5 时钟</h2> </header> <div class="clocks"> <canvas id="canvas" width="500" height="500"></canvas> </div> </body></html>Javascript 代码
// inner variablesvar canvas, ctx;var clockRadius = 250;var clockImage;// draw functions :function clear() { // clear canvas function ctx.clearRect(0, 0, ctx.canvas.width, ctx.canvas.height);}function drawScene() { // main drawScene function clear(); // clear canvas // get current time var date = new Date(); var hours = date.getHours(); var minutes = date.getMinutes(); var seconds = date.getSeconds(); hours = hours > 12 ? hours - 12 : hours; var hour = hours + minutes / 60; var minute = minutes + seconds / 60; // save current context ctx.save(); // draw clock image (as background) ctx.drawImage(clockImage, 0, 0, 500, 500); ctx.translate(canvas.width / 2, canvas.height / 2); ctx.beginPath(); // draw numbers ctx.font = '36px Arial'; ctx.fillStyle = '#000'; ctx.textAlign = 'center'; ctx.textBaseline = 'middle'; for (var n = 1; n <= 12; n++) { var theta = (n - 3) * (Math.PI * 2) / 12; var x = clockRadius * 0.7 * Math.cos(theta); var y = clockRadius * 0.7 * Math.sin(theta); ctx.fillText(n, x, y); } // draw hour ctx.save(); var theta = (hour - 3) * 2 * Math.PI / 12; ctx.rotate(theta); ctx.beginPath(); ctx.moveTo(-15, -5); ctx.lineTo(-15, 5); ctx.lineTo(clockRadius * 0.5, 1); ctx.lineTo(clockRadius * 0.5, -1); ctx.fill(); ctx.restore(); // draw minute ctx.save(); var theta = (minute - 15) * 2 * Math.PI / 60; ctx.rotate(theta); ctx.beginPath(); ctx.moveTo(-15, -4); ctx.lineTo(-15, 4); ctx.lineTo(clockRadius * 0.8, 1); ctx.lineTo(clockRadius * 0.8, -1); ctx.fill(); ctx.restore(); // draw second ctx.save(); var theta = (seconds - 15) * 2 * Math.PI / 60; ctx.rotate(theta); ctx.beginPath(); ctx.moveTo(-15, -3); ctx.lineTo(-15, 3); ctx.lineTo(clockRadius * 0.9, 1); ctx.lineTo(clockRadius * 0.9, -1); ctx.fillStyle = '#0f0'; ctx.fill(); ctx.restore(); ctx.restore();}// initialization$(function(){ canvas = document.getElementById('canvas'); ctx = canvas.getContext('2d'); // var width = canvas.width; // var height = canvas.height;clockImage = new Image();clockImage.src = 'images/2021/07/13/07/2021071307454312025062.png'; setInterval(drawScene, 1000); // loop drawScene});