JavaScript twenn动画数学计算

var moveType = {
    /*直线运动*///当前时间*变化量/持续时间+初始值
    line: function(t,b,c,d){ return c*t/d + b; },

    /*减速中最长用的是4、6、7*/
    jiansu1: {//二次方的缓动（t^2）；
        starIn: function(t,b,c,d){
            return c*(t/=d)*t + b;
        },
        starOut: function(t,b,c,d){
            return -c *(t/=d)*(t-2) + b;
        },
        starInOut: function(t,b,c,d){
            if ((t/=d/2) < 1) return c/2*t*t + b;
            return -c/2 * ((--t)*(t-2) - 1) + b;
        }
    },
    jiansu2: {//三次方的缓动（t^3）
        starIn: function(t,b,c,d){
            return c*(t/=d)*t*t + b;
        },
        starOut: function(t,b,c,d){
            return c*((t=t/d-1)*t*t + 1) + b;
        },
        starInOut: function(t,b,c,d){
            if ((t/=d/2) < 1) return c/2*t*t*t + b;
            return c/2*((t-=2)*t*t + 2) + b;
        }
    },
    jiansu3: {//四次方的缓动（t^4）；
        starIn: function(t,b,c,d){
            return c*(t/=d)*t*t*t + b;
        },
        starOut: function(t,b,c,d){
            return -c * ((t=t/d-1)*t*t*t - 1) + b;
        },
        starInOut: function(t,b,c,d){
            if ((t/=d/2) < 1) return c/2*t*t*t*t + b;
            return -c/2 * ((t-=2)*t*t*t - 2) + b;
        }
    },
    jiansu4: {//5次方的缓动（t^5）；
        starIn: function(t,b,c,d){
            return c*(t/=d)*t*t*t*t + b;
        },
        starOut: function(t,b,c,d){
            return c*((t=t/d-1)*t*t*t*t + 1) + b;
        },
        starInOut: function(t,b,c,d){
            if ((t/=d/2) < 1) return c/2*t*t*t*t*t + b;
            return c/2*((t-=2)*t*t*t*t + 2) + b;
        }
    },
    jiansu5: {//正弦曲线的缓动（sin(t)）
        starIn: function(t,b,c,d){
            return -c * Math.cos(t/d * (Math.PI/2)) + c + b;
        },
        starOut: function(t,b,c,d){
            return c * Math.sin(t/d * (Math.PI/2)) + b;
        },
        starInOut: function(t,b,c,d){
            return -c/2 * (Math.cos(Math.PI*t/d) - 1) + b;
        }
    },
    jiansu6: {//指数曲线的缓动（2^t）；
        starIn: function(t,b,c,d){
            return (t==0) ? b : c * Math.pow(2, 10 * (t/d - 1)) + b;
        },
        starOut: function(t,b,c,d){
            return (t==d) ? b+c : c * (-Math.pow(2, -10 * t/d) + 1) + b;
        },
        starInOut: 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;
        }
    },
    jiansu7: {//圆形曲线的缓动（sqrt(1-t^2)）；
        starIn: function(t,b,c,d){
            return -c * (Math.sqrt(1 - (t/=d)*t) - 1) + b;
        },
        starOut: function(t,b,c,d){
            return c * Math.sqrt(1 - (t=t/d-1)*t) + b;
        },
        starInOut: function(t,b,c,d){
            if ((t/=d/2) < 1) return -c/2 * (Math.sqrt(1 - t*t) - 1) + b;
            return c/2 * (Math.sqrt(1 - (t-=2)*t) + 1) + b;
        }
    },
    /*大摆动的效果，非常绚丽;比xiaobai好*/
    dabai: {//指数衰减的正弦曲线缓动；
        starIn: 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/(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;
        },
        starOut: 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/(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);
        },
        starInOut: function(t,b,c,d,a,p){
            if (t==0) return b;  if ((t/=d/2)==2) return b+c;  if (!p) p=d*(.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 -.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 )*.5 + c + b;
        }
    },
    xiaobai: {//超过范围的三次方缓动（(s+1)*t^3 - s*t^2）；
        starIn: function(t,b,c,d,s){
            if (s == undefined) s = 1.70158;
            return c*(t/=d)*t*((s+1)*t - s) + b;
        },
        starOut: 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;
        },
        starInOut: function(t,b,c,d,s){
            if (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;
        }
    },
    fantan: {//指数衰减的反弹缓动。
        starIn: function(t,b,c,d){
            return c - moveType.fantan.starOut(d-t, 0, c, d) + b;
        },
        starOut: 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 + .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;
            }
        },
        starInOut: function(t,b,c,d){
            if (t < d/2) return moveType.fantan.starIn(t*2, 0, c, d) * .5 + b;
            else return moveType.fantan.starOut(t*2-d, 0, c, d) * .5 + c*.5 + b;
        }
    }
};