javascript动画算法实例分析

Tween = { 
 Linear: function(t,b,c,d){ return ct/d + b; },
 Quad: {
  easeIn: function(t,b,c,d){
   return c(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) return c/2tt + b;
   return -c/2  ((--t)(t-2) - 1) + b;
  }
 },
 Cubic: {
  easeIn: function(t,b,c,d){
   return c(t/=d)tt + b;
  },
  easeOut: function(t,b,c,d){
   return c((t=t/d-1)tt + 1) + b;
  },
  easeInOut: function(t,b,c,d){
   if ((t/=d/2) < 1) return c/2ttt + b;
   return c/2((t-=2)tt + 2) + b;
  }
 },
 Quart: {
  easeIn: function(t,b,c,d){
   return c(t/=d)ttt + b;
  },
  easeOut: function(t,b,c,d){
   return -c  ((t=t/d-1)ttt - 1) + b;
  },
  easeInOut: function(t,b,c,d){
   if ((t/=d/2) < 1) return c/2tttt + b;
   return -c/2  ((t-=2)ttt - 2) + b;
  }
 },
 Quint: {
  easeIn: function(t,b,c,d){
   return c(t/=d)tttt + b;
  },
  easeOut: function(t,b,c,d){
   return c((t=t/d-1)tttt + 1) + b;
  },
  easeInOut: function(t,b,c,d){
   if ((t/=d/2) < 1) return c/2ttttt + b;
   return c/2((t-=2)tttt + 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){
   return c  Math.sin(t/d  (Math.PI/2)) + b;
  },
  easeInOut: function(t,b,c,d){
   return -c/2  (Math.cos(Math.PIt/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) return b;
   if (t==d) return b+c;
   if ((t/=d/2) < 1) return c/2  Math.pow(2, 10  (t - 1)) + b;
   return c/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){
   return c  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 - tt) - 1) + b;
   return c/2  (Math.sqrt(1 - (t-=2)t) + 1) + b;
  }
 },
 Elastic: {
  easeIn: function(t,b,c,d,a,p){
   if (t==0) return b; if ((t/=d)==1) return b+c; if (!p) p=d.3;
   if (!a || a < Math.abs(c)) { a=c; var s=p/4; }
   else var s = p/(2Math.PI)  Math.asin (c/a);
   return -(aMath.pow(2,10(t-=1))  Math.sin( (td-s)(2Math.PI)/p )) + b;
  },
  easeOut: function(t,b,c,d,a,p){
   if (t==0) return b; if ((t/=d)==1) return b+c; if (!p) p=d.3;
   if (!a || a < Math.abs(c)) { a=c; var s=p/4; }
   else var s = p/(2Math.PI)  Math.asin (c/a);
   return (aMath.pow(2,-10t)  Math.sin( (td-s)(2Math.PI)/p ) + c + b);
  },
  easeInOut: function(t,b,c,d,a,p){
   if (t==0) return b; if ((t/=d/2)==2) return b+c; if (!p) p=d(.31.5);
   if (!a || a < Math.abs(c)) { a=c; var s=p/4; }
   else var s = p/(2Math.PI)  Math.asin (c/a);
   if (t < 1) return -.5(aMath.pow(2,10(t-=1))  Math.sin( (td-s)(2Math.PI)/p )) + b;
   return aMath.pow(2,-10(t-=1))  Math.sin( (td-s)(2Math.PI)/p ).5 + c + b;
  }
 },
 Back: {
  easeIn: function(t,b,c,d,s){
   if (s == undefined) s = 1.70158;
   return c(t/=d)t((s+1)t - s) + b;
  },
  easeOut: function(t,b,c,d,s){
   if (s == undefined) s = 1.70158;
   return c((t=t/d-1)t((s+1)t + s) + 1) + b;
  },
  easeInOut: function(t,b,c,d,s){
   if (s == undefined) s = 1.70158; 
   if ((t/=d/2) < 1) return c/2(tt(((s=(1.525))+1)t - s)) + b;
   return c/2((t-=2)t(((s=(1.525))+1)t + s) + 2) + b;
  }
 },
 Bounce: {
  easeIn: function(t,b,c,d){
   return c - Tween.Bounce.easeOut(d-t, 0, c, d) + b;
  },
  easeOut: function(t,b,c,d){
   if ((t/=d) < (1/2.75)) {
    return c(7.5625tt) + b;
   } else if (t < (2/2.75)) {
    return c(7.5625(t-=(1.5/2.75))t + .75) + b;
   } else if (t < (2.5/2.75)) {
    return c(7.5625(t-=(2.25/2.75))t + .9375) + b;
   } else {
    return c(7.5625(t-=(2.625/2.75))t + .984375) + b;
   }
  },
  easeInOut: function(t,b,c,d){
   if (t < d/2) return Tween.Bounce.easeIn(t2, 0, c, d)  .5 + b;
   else return Tween.Bounce.easeOut(t2-d, 0, c, d)  .5 + c.5 + b;
  }
 }
}