Tween公式 4个参数
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） return （目标点）
1 var Tween = {
2 linear: function (t, b, c, d){ //匀速
3 return c*t/d + b;
4 },
5 easeIn: function(t, b, c, d){ //加速曲线
6 return c*(t/=d)*t + b;
7 },
8 easeOut: function(t, b, c, d){ //减速曲线
9 return -c *(t/=d)*(t-2) + b;
10 },
11 easeBoth: function(t, b, c, d){ //加速减速曲线
12 if ((t/=d/2) < 1) {
13 return c/2*t*t + b;
14 }
15 return -c/2 * ((--t)*(t-2) - 1) + b;
16 },
17 easeInStrong: function(t, b, c, d){ //加加速曲线
18 return c*(t/=d)*t*t*t + b;
19 },
20 easeOutStrong: function(t, b, c, d){ //减减速曲线
21 return -c * ((t=t/d-1)*t*t*t - 1) + b;
22 },
23 easeBothStrong: function(t, b, c, d){ //加加速减减速曲线
24 if ((t/=d/2) < 1) {
25 return c/2*t*t*t*t + b;
26 }
27 return -c/2 * ((t-=2)*t*t*t - 2) + b;
28 },
29 elasticIn: function(t, b, c, d, a, p){ //正弦衰减曲线（弹动渐入）
30 if (t === 0) {
31 return b;
32 }
33 if ( (t /= d) == 1 ) {
34 return b+c;
35 }
36 if (!p) {
37 p=d*0.3;
38 }
39 if (!a || a < Math.abs(c)) {
40 a = c;
41 var s = p/4;
42 } else {
43 var s = p/(2*Math.PI) * Math.asin (c/a);
44 }
45 return -(a*Math.pow(2,10*(t-=1)) * Math.sin( (t*d-s)*(2*Math.PI)/p )) + b;
46 },
47 elasticOut: function(t, b, c, d, a, p){ //正弦增强曲线（弹动渐出）
48 if (t === 0) {
49 return b;
50 }
51 if ( (t /= d) == 1 ) {
52 return b+c;
53 }
54 if (!p) {
55 p=d*0.3;
56 }
57 if (!a || a < Math.abs(c)) {
58 a = c;
59 var s = p / 4;
60 } else {
61 var s = p/(2*Math.PI) * Math.asin (c/a);
62 }
63 return a*Math.pow(2,-10*t) * Math.sin( (t*d-s)*(2*Math.PI)/p ) + c + b;
64 },
65 elasticBoth: function(t, b, c, d, a, p){
66 if (t === 0) {
67 return b;
68 }
69 if ( (t /= d/2) == 2 ) {
70 return b+c;
71 }
72 if (!p) {
73 p = d*(0.3*1.5);
74 }
75 if ( !a || a < Math.abs(c) ) {
76 a = c;
77 var s = p/4;
78 }
79 else {
80 var s = p/(2*Math.PI) * Math.asin (c/a);
81 }
82 if (t < 1) {
83 return - 0.5*(a*Math.pow(2,10*(t-=1)) *
84 Math.sin( (t*d-s)*(2*Math.PI)/p )) + b;
85 }
86 return a*Math.pow(2,-10*(t-=1)) *
87 Math.sin( (t*d-s)*(2*Math.PI)/p )*0.5 + c + b;
88 },
89 backIn: function(t, b, c, d, s){ //回退加速（回退渐入）
90 if (typeof s == 'undefined') {
91 s = 1.70158;
92 }
93 return c*(t/=d)*t*((s+1)*t - s) + b;
94 },
95 backOut: function(t, b, c, d, s){
96 if (typeof s == 'undefined') {
97 s = 3.70158; //回缩的距离
98 }
99 return c*((t=t/d-1)*t*((s+1)*t + s) + 1) + b;
100 },
101 backBoth: function(t, b, c, d, s){
102 if (typeof s == 'undefined') {
103 s = 1.70158;
104 }
105 if ((t /= d/2 ) < 1) {
106 return c/2*(t*t*(((s*=(1.525))+1)*t - s)) + b;
107 }
108 return c/2*((t-=2)*t*(((s*=(1.525))+1)*t + s) + 2) + b;
109 },
110 bounceIn: function(t, b, c, d){ //弹球减振（弹球渐出）
111 return c - Tween['bounceOut'](d-t, 0, c, d) + b;
112 },
113 bounceOut: function(t, b, c, d){
114 if ((t/=d) < (1/2.75)) {
115 return c*(7.5625*t*t) + b;
116 } else if (t < (2/2.75)) {
117 return c*(7.5625*(t-=(1.5/2.75))*t + 0.75) + b;
118 } else if (t < (2.5/2.75)) {
119 return c*(7.5625*(t-=(2.25/2.75))*t + 0.9375) + b;
120 }
121 return c*(7.5625*(t-=(2.625/2.75))*t + 0.984375) + b;
122 },
123 bounceBoth: function(t, b, c, d){
124 if (t < d/2) {
125 return Tween['bounceIn'](t*2, 0, c, d) * 0.5 + b;
126 }
127 return Tween['bounceOut'](t*2-d, 0, c, d) * 0.5 + c*0.5 + b;
128 }
129 }