<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>随机萤火虫</title>
<style type="text/css">
*{
margin: 0;
padding: 0;
}
body,html{
height: 100%;
width: 100%;
}
#bg{
width: 100%;
height: 100%;
background: url(img/bg.jpg) no-repeat;
background-size: cover;
}
img{
display: block;
position: absolute;
top: 0;
left: 0;
}
</style>
</head>
<body>
<script src="js/Tween.js" type="text/javascript" charset="utf-8"></script>
<div id="bg"></div>
<script type="text/javascript">
//构造函数
function Firefly(){
this.oBg = document.getElementById("bg");
this.oImg = document.createElement('img');
}
//给新创建的萤火虫设置大小、位置
Firefly.prototype.occur = function(){
this.oImg.src = 'img/star.jpg';
this.oImg.style.width = this.oWidth + 'px';
this.oImg.style.height = this.oWidth + 'px';
this.oImg.style.top = this.oTop + 'px';
this.oImg.style.left = this.oLeft + 'px';
this.oBg.appendChild( this.oImg );
return this;
}
//获取萤火虫的随机位置、大小
Firefly.prototype.randomPlace = function(){
this.oLeft = this.randomNUm( window.innerWidth - 50 );
this.oTop = this.randomNUm( window.innerHeight - 50 );
this.oWidth = this.randomNUm(20) + 12;
return this;
}
//飞行时间控制在5-10秒
Firefly.prototype.flyTime = function(){
this.oTime = Math.floor( Math.random() * 5 + 5 ) * 1000;
return this;
}
//调用运动函数使萤火虫飞行
Firefly.prototype.fly = function(){
var This = this;
this.oImg.sport( This.oImg , {'top':this.oTop,'left':this.oLeft} , this.oTime ,function(){
This.flyTime().occur().randomPlace().fly();
} );
}
//构造一个范围内的随机数
Firefly.prototype.randomNUm = function( num ){
return Math.floor( Math.random()*num );
}
var fireFly = [];
for( var i = 0;i<50;i++ )
{
//构造50个萤火虫
fireFly[i] = new Firefly();
fireFly[i].randomPlace().flyTime().occur().randomPlace().fly();
}
</script>
</body>
</html>//Tween.js代码
Object.prototype.sport = function( obj , Json , time , ev , fn ){
if ( typeof ev == 'undefined' )
{
time = time || 400;
ev = 'linear';
}
if ( typeof time == 'string' )
{
fn = ev;
ev = time;
time = 400;
}else if ( typeof time == 'number' && typeof ev == 'function' )
{
fn = ev;
ev = 'linear';
}else if ( typeof time == 'function' )
{
fn = time;
time = 400;
ev = 'linear';
}
var This = this;
var oB = {};
for( attr in Json )
{
oB[attr] = parseInt( this.getStyle( this , attr ) );
}
var oC = {};
for( attr in Json )
{
oC[attr] = Json[attr];
}
var startTime = new Date().getTime();
clearInterval( this.timer );
obj.timer = setInterval( function(){
var nowTime = new Date().getTime();
var time2 = Math.min(nowTime - startTime , time);
for( attr in Json ) //t,b,c,d
{
var oChange = Tween[ev]( time2 , oB[attr] , oC[attr] - oB[attr] , time );
if( attr == 'opacity' )
{
obj.style[attr] = oChange;
obj.style.filter = 'alpha(opacity='+(oChange*100)+')';
}else{
obj.style[attr] = oChange + 'px';
}
}
if( time2 == time )
{
clearInterval( obj.timer );
fn && fn( This );
}
} ,30 );
}
Object.prototype.getStyle = function( obj , att ){
return obj.currentStyle ? obj.currentStyle[att] : getComputedStyle( obj )[att];
}
var Tween = {
linear: function (t, b, c, d){ //匀速
return c*t/d + b;
},
easeIn: function(t, b, c, d){ //加速曲线
return c*(t/=d)*t + b;
},
easeOut: function(t, b, c, d){ //减速曲线
return -c *(t/=d)*(t-2) + b;
},
easeBoth: function(t, b, c, d){ //加速减速曲线
if ((t/=d/2) < 1) {
return c/2*t*t + b;
}
return -c/2 * ((--t)*(t-2) - 1) + b;
},
easeInStrong: function(t, b, c, d){ //加加速曲线
return c*(t/=d)*t*t*t + b;
},
easeOutStrong: function(t, b, c, d){ //减减速曲线
return -c * ((t=t/d-1)*t*t*t - 1) + b;
},
easeBothStrong: function(t, b, c, d){ //加加速减减速曲线
if ((t/=d/2) < 1) {
return c/2*t*t*t*t + b;
}
return -c/2 * ((t-= 2)*t*t*t - 2) + b;
},
elasticIn: function(t, b, c, d, a, p){ //正弦衰减曲线（弹动渐入）
if (t === 0) {
return b;
}
if ( (t /= d) == 1 ) {
return b+c;
}
if (!p) {
p=d*0.3;
}
if (!a || a < Math.abs(c)) {
a = c;
var s = p/4;
} else {
var s = p/(2*Math.PI) * Math.asin (c/a);
}
return -(a*Math.pow(2,10*(t-= 1)) * Math.sin( (t*d-s)*(2*Math.PI)/p )) + b;
},
elasticOut: function(t, b, c, d, a, p){ //正弦增强曲线（弹动渐出）
if (t === 0) {
return b;
}
if ( (t /= d) == 1 ) {
return b+c;
}
if (!p) {
p=d*0.3;
}
if (!a || a < Math.abs(c)) {
a = c;
var s = p / 4;
} else {
var s = p/(2*Math.PI) * Math.asin (c/a);
}
return a*Math.pow(2,-10*t) * Math.sin( (t*d-s)*(2*Math.PI)/p ) + c + b;
},
elasticBoth: function(t, b, c, d, a, p){
if (t === 0) {
return b;
}
if ( (t /= d/2) == 2 ) {
return b+c;
}
if (!p) {
p = d*(0.3*1.5);
}
if ( !a || a < Math.abs(c) ) {
a = c;
var s = p/4;
}
else {
var s = p/(2*Math.PI) * Math.asin (c/a);
}
if (t < 1) {
return - 0.5*(a*Math.pow(2,10*(t-= 1)) *
Math.sin( (t*d-s)*(2*Math.PI)/p )) + b;
}
return a*Math.pow(2,-10*(t-= 1)) *
Math.sin( (t*d-s)*(2*Math.PI)/p )*0.5 + c + b;
},
backIn: function(t, b, c, d, s){ //回退加速（回退渐入）
if (typeof s == 'undefined') {
s = 1.70158;
}
return c*(t/=d)*t*((s+1)*t - s) + b;
},
backOut: function(t, b, c, d, s){
if (typeof s == 'undefined') {
s = 3.70158; //回缩的距离
}
return c*((t=t/d-1)*t*((s+1)*t + s) + 1) + b;
},
backBoth: function(t, b, c, d, s){
if (typeof s == 'undefined') {
s = 1.70158;
}
if ((t /= d/2 ) < 1) {
return c/2*(t*t*(((s*=(1.525))+1)*t - s)) + b;
}
return c/2*((t-= 2)*t*(((s*=(1.525))+1)*t + s) + 2) + b;
},
bounceIn: function(t, b, c, d){ //弹球减振（弹球渐出）
return c - Tween['bounceOut'](d-t, 0, c, d) + b;
},
bounceOut: function(t, b, c, d){
if ((t/=d) < (1/2.75)) {
return c*(7.5625*t*t) + b;
} else if (t < (2/2.75)) {
return c*(7.5625*(t-=(1.5/2.75))*t + 0.75) + b;
} else if (t < (2.5/2.75)) {
return c*(7.5625*(t-=(2.25/2.75))*t + 0.9375) + b;
}
return c*(7.5625*(t-=(2.625/2.75))*t + 0.984375) + b;
},
bounceBoth: function(t, b, c, d){
if (t < d/2) {
return Tween['bounceIn'](t*2, 0, c, d) * 0.5 + b;
}
return Tween['bounceOut'](t*2-d, 0, c, d) * 0.5 + c*0.5 + b;
}
}
来源：http://www.cnblogs.com/lijiahui199494/p/5855200.html