本文实例为大家分享了JS实现动态星空背景的具体代码，供大家参考，具体内容如下

这里我截取的是一个图片，实际上是会动的。废话不多说，上代码。

HTML：

CSS：

/*css reset */

body,p,div,ol,ul,li,dl,dt,dd,h1,h2,h3,h4,h5,h6,form,input,iframe,nav {

margin: 0;

padding: 0;

}

html,body {

width: 100%;

height: 100%;

}

body {

font: 14px Microsoft YaHei;

-webkit-text-size-adjust:100%;

-moz-user-select: none;

-webkit-user-select: none;

user-select: none;

position: relative;

background: #000;

}

#canvas {

width: 100%;

height: 100%;

display: block;

opacity: .8;

}

JS：

// 音量大小,0.01-1

//宇宙特效

var canvas = document.getElementById('canvas'),

ctx = canvas.getContext('2d'),

w = canvas.width = window.innerWidth,

h = canvas.height = window.innerHeight,

hue = 217,

stars = [],

count = 0,

maxStars = 1100; //星星数量,默认1300

var canvas2 = document.createElement('canvas'),

ctx2 = canvas2.getContext('2d');

canvas2.width = 100;

canvas2.height = 100;

var half = canvas2.width / 2,

gradient2 = ctx2.createRadialGradient(half, half, 0, half, half, half);

gradient2.addColorStop(0.025, '#CCC');

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();

ctx2.arc(half, half, half, 0, Math.PI * 2);

ctx2.fill();

// End cache

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;

}

function maxOrbit(x, y) {

var max = Math.max(x, y),

diameter = Math.round(Math.sqrt(max * max + max * max));

return diameter / 2;

//星星移动范围，值越大范围越小，

}

var Star = function() {

this.orbitRadius = random(maxOrbit(w, h));

this.radius = random(60, this.orbitRadius) / 10; //星星大小,值越大星星越小,默认8

this.orbitX = w / 2;

this.orbitY = h / 2;

this.timePassed = random(0, maxStars);

this.speed = random(this.orbitRadius) / 80000; //星星移动速度,值越大越慢,默认5W

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 = 0.5; //尾巴

ctx.fillStyle = 'hsla(' + hue + ', 64%, 6%, 2)';

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();

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。