<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>雪花</title>
<style>
html,body{ margin: 0; height: 100%; background-color: #151515; }
body{ background-image: url(img/bg.jpg); background-position: center center; background-repeat: no-repeat; background-color: #0D0B18; }
#snowBox{position: relative;width: 100%;height: 100%;margin: 0 auto;/*background: #33EAE8;*/overflow: hidden;}
.snowFlake{position: absolute;}
</style>
</head>
<body>
<div id="snowBox"></div>
<script>
//判断IE
function isIE(){
var b = document.createElement('b');
b.innerHTML = '<!--[if lte IE 8]><i></i><![endif]-->';
return b.getElementsByTagName('i').length === 1;
};
//定义雪花
function CreateSnow(snowBox,src,style){
this.snowBox = document.getElementById(snowBox);//找到容器
this.snowStyle = Math.ceil(Math.random()*style);//雪花类型[1,2]
this.maxLeft = this.snowBox.offsetWidth-Math.random()*5+3;//运动范围
this.maxTop = this.snowBox.offsetHeight-Math.random()*5+3;
this.left = this.snowBox.offsetWidth*Math.random();//起始位置
this.top = this.snowBox.offsetHeight*Math.random();
this.angle=1.1+0.8*Math.random();//飘落角度
this.minAngle=1.1;
this.maxAngle=1.9;
this.angleDelta=0.01*Math.random();
this.speed=1.4+Math.random();//下落速度
this.createEle(src);//制作雪花dom 凹=放在最后，使得原型里能取到值
};
//雪片生成+下落
CreateSnow.prototype = {
createEle : function(baseSrc){//生成雪花元素
var srcIndex = baseSrc.lastIndexOf('.'),//获取最后一个'.'
src = baseSrc.substring(0,srcIndex)+this.snowStyle+baseSrc.substring(srcIndex,baseSrc.length);
var image = new Image();
image.src = src;
this.ele = document.createElement("img");
this.ele.setAttribute('src',src);
this.ele.style.position="absolute";
this.ele.style.zIndex="99";
this.snowBox.appendChild(this.ele);
//设置雪花尺寸
var img = this.ele;
image.onload = function(){
imgW = image.width;
img.setAttribute('width',Math.ceil(imgW*(0.1+Math.random())));
if(isIE()){//如果旧IE，设置高度
imgH = image.height;
img.setAttribute('height',Math.ceil(imgH*(0.1+Math.random())));
}
};
},
move : function(){//雪花运动
if(this.angle< this.minAngle||this.angle>this.maxAngle){
this.angleDelta=-this.angleDelta;
}
this.angle+=this.angleDelta;
this.left+=this.speed*Math.cos(this.angle*Math.PI);
this.top-=this.speed*Math.sin(this.angle*Math.PI);
if(this.left<0){
this.left=this.maxLeft;
}else if(this.left>this.maxLeft){
this.left=0
}
if(this.top>this.maxTop){//雪花掉出来后回到顶部
this.top=0;
}
this.ele.style.left=this.left+'px';//凹=加‘px’
this.ele.style.top=this.top+'px';
}
};
//下雪启动
function goSnow(snowBox,src,num,style){
var snowArr = [];
for(var j = 0 ; j<num ; j++){
snowArr.push(new CreateSnow(snowBox,src,style));
}
var makeSnowtime = setInterval(function(){
for(var i = snowArr.length-1;i>=0;i--){//找到数组中的最新的一个
if(snowArr[i]){
snowArr[i].move();
}
}
},40);
};
//初始化加载
window.onload = function(){
var snowBox = 'snowBox',//雪花容器
src = './img/snow.png',//雪花图基本命名<图片名就是snow+1/2/3/4...>
num = 20,//雪花数量
style = 2;//图片种类数
goSnow(snowBox,src,num,style);
};
</script>
</body>
</html>
