代码如下：
<!doctype html> <html> <head> <meta charset="utf-8"> <title>星空背景代码实现</title> <script src="https://libs.baidu.com/jquery/1.11.3/jquery.min.js"></script> <style type="text/css"> #canvas{ position: absolute; z-index: -1; left: 0; top: 0; } .main{ position: absolute; z-index: 2; top: 0; left: 0; } h1{ color: #FFFFFF; } </style> </head> <body> <div id="main"> <h1>canvas</h1> </div> <!-- 1、简要介绍 canvas 绘制 js代码 2、如何用来做背景 z-index 什么情况下才有用 3、弹性盒子作浮动元素居中 display: flex; align-items: center; justify-content: center; 4、下载网址 https://www.jq22.com/ --> <canvas id="canvas"></canvas> <script> var canvas = document.getElementById('canvas'), ctx = canvas.getContext('2d'), w = canvas.width = window.innerWidth, h = canvas.height = window.innerHeight, hue = 217, // 十六进制颜色 stars = [], count = 0, maxStars = 1200; // 星星的数量 var canvas2 = document.createElement('canvas'), ctx2 = canvas2.getContext('2d'); canvas2.width = 100; canvas2.height = 100; var half = canvas2.width / 2, // 绘制一个矩形，并用放射状/圆形渐变进行填充：(x0,y0,r0,x1,y1,r1) gradient2 = ctx2.createRadialGradient(half, half, 0, half, half, half); // gradient.addColorStop(stop 0~1,color); gradient2.addColorStop(0.025, '#fff'); gradient2.addColorStop(0.1, 'hsl(' + hue + ', 61%, 33%)'); gradient2.addColorStop(0.25, 'hsl(' + hue + ', 64%, 6%)'); gradient2.addColorStop(1, 'transparent'); ctx2.fillStyle = gradient2; ctx2.beginPath(); // 起始一条路径，或重置当前路径 ctx2.arc(half, half, half, 0, Math.PI * 2); ctx2.fill(); // 填充当前绘制（路径） // canvas 绘制的大小 $(window).resize(function () { w = canvas.width = window.innerWidth; h = canvas.height = window.innerHeight; canvas.width(w).height(h); }); // 最大 和 最小星星的 随机位置 function random(min, max) { if (arguments.length < 2) { max = min; min = 0; } if (min > max) { var hold = max; max = min; min = hold; } return Math.floor(Math.random() * (max - min + 1)) + min; } // 最大和最小的 星星 function maxOrbit(x, y) { var max = Math.max(x, y), diameter = Math.round(Math.sqrt(max * max + max * max)); return diameter / 2; } var Star = function () { this.orbitRadius = random(maxOrbit(w, h)); this.radius = random(60, this.orbitRadius) / 12; this.orbitX = w / 2; this.orbitY = h / 2; this.timePassed = random(0, maxStars); this.speed = random(this.orbitRadius) / 900000; this.alpha = random(2, 10) / 10; count++; stars[count] = this; } Star.prototype.draw = function () { var x = Math.sin(this.timePassed) * this.orbitRadius + this.orbitX, y = Math.cos(this.timePassed) * this.orbitRadius + this.orbitY, twinkle = random(10); if (twinkle === 1 && this.alpha > 0) { this.alpha -= 0.05; } else if (twinkle === 2 && this.alpha < 1) { this.alpha += 0.05; } ctx.globalAlpha = this.alpha; ctx.drawImage(canvas2, x - this.radius / 2, y - this.radius / 2, this.radius, this.radius); this.timePassed += this.speed; } for (var i = 0; i < maxStars; i++) { new Star(); } function animation() { ctx.globalCompositeOperation = 'source-over'; ctx.globalAlpha = 0.8; ctx.fillStyle = 'hsla(' + hue + ', 64%, 6%, 1)'; ctx.fillRect(0, 0, w, h) ctx.globalCompositeOperation = 'lighter'; for (var i = 1, l = stars.length; i < l; i++) { stars[i].draw(); }; window.requestAnimationFrame(animation); } animation(); </script> </body> </html>