js实现下雪雪花特效
两种下雪特效：
1.
<script type="text/javascript"> (function($){ $.fn.snow = function(options){ var $flake = $('<div id="snowbox" />').css({'position': 'absolute','z-index':'9999', 'top': '-50px'}).html('❄'), documentHeight = $(document).height(), documentWidth = $(document).width(), defaults = { minSize : 10, maxSize : 20, newOn : 1000, flakeColor : "#AFDAEF" /* 此处可以定义雪花颜色，若要白色可以改为#FFFFFF */ }, options = $.extend({}, defaults, options); var interval= setInterval( function(){ var startPositionLeft = Math.random() * documentWidth - 100, startOpacity = 0.5 + Math.random(), sizeFlake = options.minSize + Math.random() * options.maxSize, endPositionTop = documentHeight - 200, endPositionLeft = startPositionLeft - 500 + Math.random() * 500, durationFall = documentHeight * 10 + Math.random() * 5000; $flake.clone().appendTo('body').css({ left: startPositionLeft, opacity: startOpacity, 'font-size': sizeFlake, color: options.flakeColor }).animate({ top: endPositionTop, left: endPositionLeft, opacity: 0.2 },durationFall,'linear',function(){ $(this).remove() }); }, options.newOn); }; })(jQuery); $(function(){ $.fn.snow({ minSize: 5, /* 定义雪花最小尺寸 */ maxSize: 50,/* 定义雪花最大尺寸 */ newOn: 300 /* 定义密集程度，数字越小越密集 */ }); }); </script>
2.
<script type="text/javascript">
/* 控制下雪 */
function snowFall(snow) {
/* 可配置属性 */
snow = snow || {};
this.maxFlake = snow.maxFlake || 200; /* 最多片数 */
this.flakeSize = snow.flakeSize || 10; /* 雪花形状 */
this.fallSpeed = snow.fallSpeed || 1; /* 坠落速度 */
}
/* 兼容写法 */
requestAnimationFrame = window.requestAnimationFrame ||
window.mozRequestAnimationFrame ||
window.webkitRequestAnimationFrame ||
window.msRequestAnimationFrame ||
window.oRequestAnimationFrame ||
function(callback) { setTimeout(callback, 1000 / 60); };
cancelAnimationFrame = window.cancelAnimationFrame ||
window.mozCancelAnimationFrame ||
window.webkitCancelAnimationFrame ||
window.msCancelAnimationFrame ||
window.oCancelAnimationFrame;
/* 开始下雪 */
snowFall.prototype.start = function(){
/* 创建画布 */
snowCanvas.apply(this);
/* 创建雪花形状 */
createFlakes.apply(this);
/* 画雪 */
drawSnow.apply(this)
}
/* 创建画布 */
function snowCanvas() {
/* 添加Dom结点 */
var snowcanvas = document.createElement("canvas");
snowcanvas.id = "snowfall";
snowcanvas.width = window.innerWidth;
snowcanvas.height = document.body.clientHeight;
snowcanvas.setAttribute("style", "position:absolute; top: 0; left: 0; z-index: 1; pointer-events: none;");
document.getElementsByTagName("body")[0].appendChild(snowcanvas);
this.canvas = snowcanvas;
this.ctx = snowcanvas.getContext("2d");
/* 窗口大小改变的处理 */
window.onresize = function() {
snowcanvas.width = window.innerWidth;
/* snowcanvas.height = window.innerHeight */
}
}
/* 雪运动对象 */
function flakeMove(canvasWidth, canvasHeight, flakeSize, fallSpeed) {
this.x = Math.floor(Math.random() * canvasWidth); /* x坐标 */
this.y = Math.floor(Math.random() * canvasHeight); /* y坐标 */
this.size = Math.random() * flakeSize + 2; /* 形状 */
this.maxSize = flakeSize; /* 最大形状 */
this.speed = Math.random() * 1 + fallSpeed; /* 坠落速度 */
this.fallSpeed = fallSpeed; /* 坠落速度 */
this.velY = this.speed; /* Y方向速度 */
this.velX = 0; /* X方向速度 */
this.stepSize = Math.random() / 30; /* 步长 */
this.step = 0 /* 步数 */
}
flakeMove.prototype.update = function() {
var x = this.x,
y = this.y;
/* 左右摆动(余弦) */
this.velX *= 0.98;
if (this.velY <= this.speed) {
this.velY = this.speed
}
this.velX += Math.cos(this.step += .05) * this.stepSize;
this.y += this.velY;
this.x += this.velX;
/* 飞出边界的处理 */
if (this.x >= canvas.width || this.x <= 0 || this.y >= canvas.height || this.y <= 0) {
this.reset(canvas.width, canvas.height)
}
};
/* 飞出边界-放置最顶端继续坠落 */
flakeMove.prototype.reset = function(width, height) {
this.x = Math.floor(Math.random() * width);
this.y = 0;
this.size = Math.random() * this.maxSize + 2;
this.speed = Math.random() * 1 + this.fallSpeed;
this.velY = this.speed;
this.velX = 0;
};
// 渲染雪花-随机形状（此处可修改雪花颜色！！！）
flakeMove.prototype.render = function(ctx) {
var snowFlake = ctx.createRadialGradient(this.x, this.y, 0, this.x, this.y, this.size);
snowFlake.addColorStop(0, "rgba(255, 255, 255, 0.9)"); /* 此处是雪花颜色，默认是白色 */
snowFlake.addColorStop(.5, "rgba(255, 255, 255, 0.5)"); /* 若要改为其他颜色，请自行查 */
snowFlake.addColorStop(1, "rgba(255, 255, 255, 0)"); /* 找16进制的RGB 颜色代码。 */
ctx.save();
ctx.fillStyle = snowFlake;
ctx.beginPath();
ctx.arc(this.x, this.y, this.size, 0, Math.PI * 2);
ctx.fill();
ctx.restore();
};
/* 创建雪花-定义形状 */
function createFlakes() {
var maxFlake = this.maxFlake,
flakes = this.flakes = [],
canvas = this.canvas;
for (var i = 0; i < maxFlake; i++) {
flakes.push(new flakeMove(canvas.width, canvas.height, this.flakeSize, this.fallSpeed))
}
}
/* 画雪 */
function drawSnow() {
var maxFlake = this.maxFlake,
flakes = this.flakes;
ctx = this.ctx, canvas = this.canvas, that = this;
/* 清空雪花 */
ctx.clearRect(0, 0, canvas.width, canvas.height);
for (var e = 0; e < maxFlake; e++) {
flakes[e].update();
flakes[e].render(ctx);
}
/* 一帧一帧的画 */
this.loop = requestAnimationFrame(function() {
drawSnow.apply(that);
});
}
/* 调用及控制方法 */
var snow = new snowFall({maxFlake:500});
snow.start();
</script>
使用方法：
方法①、复制其中一种 JS 代码，粘贴到网站</body>标签之前即可；
方法②、去掉代码前后的<script **>标签，然后将代码保存为 js 文件，最后在网站引用即可。
Ps：若没效果，请确认网页是否已载入 JQurey，如果没有请在下雪代码之前引入 JQ 即可。
