```javascript
/*
* Tween.js
* t: current time（当前时间）；
* b: beginning value（初始值）；
* c: change in value（变化量）；
* d: duration（持续时间）。
* you can visit 'http://easings.net/zh-cn' to get effect
*/
varTween={
Linear:function(t,b,c,d) {
returnc*t/d+b;
},
Quad:{
easeIn:function(t,b,c,d) {
returnc*(t/=d)*t+b;
},
easeOut:function(t,b,c,d) {
return-c*(t/=d)*(t-2)+b;
},
easeInOut:function(t,b,c,d) {
if((t/=d/2)<1)returnc/2*t*t+b;
return-c/2*((--t)*(t-2)-1)+b;
}
},
Cubic:{
easeIn:function(t,b,c,d) {
returnc*(t/=d)*t*t+b;
},
easeOut:function(t,b,c,d) {
returnc*((t=t/d-1)*t*t+1)+b;
},
easeInOut:function(t,b,c,d) {
if((t/=d/2)<1)returnc/2*t*t*t+b;
returnc/2*((t-=2)*t*t+2)+b;
}
},
Quart:{
easeIn:function(t,b,c,d) {
returnc*(t/=d)*t*t*t+b;
},
easeOut:function(t,b,c,d) {
return-c*((t=t/d-1)*t*t*t-1)+b;
},
easeInOut:function(t,b,c,d) {
if((t/=d/2)<1)returnc/2*t*t*t*t+b;
return-c/2*((t-=2)*t*t*t-2)+b;
}
},
Quint:{
easeIn:function(t,b,c,d) {
returnc*(t/=d)*t*t*t*t+b;
},
easeOut:function(t,b,c,d) {
returnc*((t=t/d-1)*t*t*t*t+1)+b;
},
easeInOut:function(t,b,c,d) {
if((t/=d/2)<1)returnc/2*t*t*t*t*t+b;
returnc/2*((t-=2)*t*t*t*t+2)+b;
}
},
Sine:{
easeIn:function(t,b,c,d) {
return-c*Math.cos(t/d*(Math.PI/2))+c+b;
},
easeOut:function(t,b,c,d) {
returnc*Math.sin(t/d*(Math.PI/2))+b;
},
easeInOut:function(t,b,c,d) {
return-c/2*(Math.cos(Math.PI*t/d)-1)+b;
}
},
Expo:{
easeIn:function(t,b,c,d) {
return(t==0)?b:c*Math.pow(2,10*(t/d-1))+b;
},
easeOut:function(t,b,c,d) {
return(t==d)?b+c:c*(-Math.pow(2,-10*t/d)+1)+b;
},
easeInOut:function(t,b,c,d) {
if(t==0)returnb;
if(t==d)returnb+c;
if((t/=d/2)<1)returnc/2*Math.pow(2,10*(t-1))+b;
returnc/2*(-Math.pow(2,-10*--t)+2)+b;
}
},
Circ:{
easeIn:function(t,b,c,d) {
return-c*(Math.sqrt(1-(t/=d)*t)-1)+b;
},
easeOut:function(t,b,c,d) {
returnc*Math.sqrt(1-(t=t/d-1)*t)+b;
},
easeInOut:function(t,b,c,d) {
if((t/=d/2)<1)return-c/2*(Math.sqrt(1-t*t)-1)+b;
returnc/2*(Math.sqrt(1-(t-=2)*t)+1)+b;
}
},
Elastic:{
easeIn:function(t,b,c,d,a,p) {
vars;
if(t==0)returnb;
if((t/=d)==1)returnb+c;
if(typeofp=="undefined") p=d*.3;
if(!a||a
s=p/4;
a=c;
}else{
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;
},
easeOut:function(t,b,c,d,a,p) {
vars;
if(t==0)returnb;
if((t/=d)==1)returnb+c;
if(typeofp=="undefined") p=d*.3;
if(!a||a
a=c;
s=p/4;
}else{
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);
},
easeInOut:function(t,b,c,d,a,p) {
vars;
if(t==0)returnb;
if((t/=d/2)==2)returnb+c;
if(typeofp=="undefined") p=d*(.3*1.5);
if(!a||a
a=c;
s=p/4;
}else{
s=p/(2*Math.PI)*Math.asin(c/a);
}
if(t<1)return-.5*(a*Math.pow(2,10*(t-=1))*Math.sin((t*d-s)*(2*Math.PI)/p))+b;
returna*Math.pow(2,-10*(t-=1))*Math.sin((t*d-s)*(2*Math.PI)/p )*.5+c+b;
}
},
Back:{
easeIn:function(t,b,c,d,s) {
if(typeofs=="undefined") s=1.70158;
returnc*(t/=d)*t*((s+1)*t-s)+b;
},
easeOut:function(t,b,c,d,s) {
if(typeofs=="undefined") s=1.70158;
returnc*((t=t/d-1)*t*((s+1)*t+s)+1)+b;
},
easeInOut:function(t,b,c,d,s) {
if(typeofs=="undefined") s=1.70158;
if((t/=d/2)<1)returnc/2*(t*t*(((s*=(1.525))+1)*t-s))+b;
returnc/2*((t-=2)*t*(((s*=(1.525))+1)*t+s)+2)+b;
}
},
Bounce:{
easeIn:function(t,b,c,d) {
returnc-Tween.Bounce.easeOut(d-t,0, c, d)+b;
},
easeOut:function(t,b,c,d) {
if((t/=d)<(1/2.75)) {
returnc*(7.5625*t*t)+b;
}elseif(t<(2/2.75)) {
returnc*(7.5625*(t-=(1.5/2.75))*t+.75)+b;
}elseif(t<(2.5/2.75)) {
returnc*(7.5625*(t-=(2.25/2.75))*t+.9375)+b;
}else{
returnc*(7.5625*(t-=(2.625/2.75))*t+.984375)+b;
}
},
easeInOut:function(t,b,c,d) {
if(t
returnTween.Bounce.easeIn(t*2,0, c, d)*.5+b;
}else{
returnTween.Bounce.easeOut(t*2-d,0, c, d)*.5+c*.5+b;
}
}
}
}
Math.tween=Tween;
```
