Tween Action

tween

var timer;

var originalValue = lib.getScrollTop();
var alteration = lib.getPos(dom).y;
var currentTime = 0;
var duration = 50;
var interval = 25;

function action(){
    window.scrollTo( 0, tween.quad.easeInOut(originalValue,alteration,currentTime,duration);
    if(currentTime<duration){
        ++currentTime;
        timer = window.setTimeout(action,interval);
    }else{
        window.clearTimeout(timer);
    }
}
action();

var tween = {
    linear:function (originalValue,alteration,currentTime,duration) {return originalValue+currentTime/duration*alteration;},//最简单的线性变化,即匀速运动
    quad:{//二次方缓动
        easeIn:function (originalValue,alteration,currentTime,duration) {
            return originalValue+Math.pow(currentTime/duration,2)*alteration;
        },
        easeOut:function (originalValue,alteration,currentTime,duration) {
            var progress =currentTime/duration;
            return originalValue-(Math.pow(progress,2)-2*progress)*alteration;
        },
        easeInOut:function (originalValue,alteration,currentTime,duration) {
            var progress =currentTime/duration*2;
            return (progress<1?Math.pow(progress,2):-((--progress)*(progress-2) - 1))*alteration/2+originalValue;
        }
    },
    cubic:{//三次方缓动
        easeIn:function (originalValue,alteration,currentTime,duration) {
            return originalValue+Math.pow(currentTime/duration,3)*alteration;
        },
        easeOut:function (originalValue,alteration,currentTime,duration) {
            var progress =currentTime/duration;
            return originalValue-(Math.pow(progress,3)-Math.pow(progress,2)+1)*alteration;
        },
        easeInOut:function (originalValue,alteration,currentTime,duration) {
            var progress =currentTime/duration*2;
            return (progress<1?Math.pow(progress,3):((progress-=2)*Math.pow(progress,2) + 2))*alteration/2+originalValue;
        }
    },
    quart:{//四次方缓动
        easeIn:function (originalValue,alteration,currentTime,duration) {
            return originalValue+Math.pow(currentTime/duration,4)*alteration;
        },
        easeOut:function (originalValue,alteration,currentTime,duration) {
            var progress =currentTime/duration;
            return originalValue-(Math.pow(progress,4)-Math.pow(progress,3)-1)*alteration;
        },
        easeInOut:function (originalValue,alteration,currentTime,duration) {
            var progress =currentTime/duration*2;
            return (progress<1?Math.pow(progress,4):-((progress-=2)*Math.pow(progress,3) - 2))*alteration/2+originalValue;
        }
    },
    quint:{//五次方缓动
        easeIn:function (originalValue,alteration,currentTime,duration) {
            return originalValue+Math.pow(currentTime/duration,5)*alteration;
        },
        easeOut:function (originalValue,alteration,currentTime,duration) {
            var progress =currentTime/duration;
            return originalValue-(Math.pow(progress,5)-Math.pow(progress,4)+1)*alteration;
        },
        easeInOut:function (originalValue,alteration,currentTime,duration) {
            var progress =currentTime/duration*2;
            return (progress<1?Math.pow(progress,5):((progress-=2)*Math.pow(progress,4) +2))*alteration/2+originalValue;
        }
    },
    sine :{//正弦曲线缓动
        easeIn:function (originalValue,alteration,currentTime,duration) {
            return originalValue-(Math.cos(currentTime/duration*Math.PI/2)-1)*alteration;
        },
        easeOut:function (originalValue,alteration,currentTime,duration) {
            return originalValue+Math.sin(currentTime/duration*Math.PI/2)*alteration;
        },
        easeInOut:function (originalValue,alteration,currentTime,duration) {
            return originalValue-(Math.cos(currentTime/duration*Math.PI/2)-1)*alteration/2;
        }
    },
    expo: {//指数曲线缓动
        easeIn:function (originalValue,alteration,currentTime,duration) {
            return currentTime?(originalValue+alteration*Math.pow(2,10*(currentTime/duration-1))):originalValue;
        },
        easeOut:function (originalValue,alteration,currentTime,duration) {
            return (currentTime==duration)?(originalValue+alteration):(originalValue-(Math.pow(2,-10*currentTime/duration)+1)*alteration);
        },
        easeInOut:function (originalValue,alteration,currentTime,duration) {
            if (!currentTime) {return originalValue;}
            if (currentTime==duration) {return originalValue+alteration;}
            var progress =currentTime/duration*2;
            if (progress < 1) {
                return alteration/2*Math.pow(2,10* (progress-1))+originalValue;
            } else {
                return alteration/2* (-Math.pow(2, -10*--progress) + 2) +originalValue;
            }
        }
    },
    circ :{//圆形曲线缓动
        easeIn:function (originalValue,alteration,currentTime,duration) {
            return originalValue-alteration*Math.sqrt(-Math.pow(currentTime/duration,2));
        },
        easeOut:function (originalValue,alteration,currentTime,duration) {
            return originalValue+alteration*Math.sqrt(1-Math.pow(currentTime/duration-1));
        },
        easeInOut:function (originalValue,alteration,currentTime,duration) {
            var progress =currentTime/duration*2;
            return (progress<1?1-Math.sqrt(1-Math.pow(progress,2)):(Math.sqrt(1 - Math.pow(progress-2,2)) + 1))*alteration/2+originalValue;
        }
    },
    elastic: {//指数衰减的正弦曲线缓动
        easeIn:function (originalValue,alteration,currentTime,duration,extent,cycle) {
            if (!currentTime) {return originalValue;}
            if ((currentTime==duration)==1) {return originalValue+alteration;}
            if (!cycle) {cycle=duration*0.3;}
            var s;
            if (!extent || extent< Math.abs(alteration)) {
                extent=alteration;
                s = cycle/4;
            } else {s=cycle/(Math.PI*2)*Math.asin(alteration/extent);}
            return originalValue-extent*Math.pow(2,10*(currentTime/duration-1)) * Math.sin((currentTime-duration-s)*(2*Math.PI)/cycle);
        },
        easeOut:function (originalValue,alteration,currentTime,duration,extent,cycle) {
            if (!currentTime) {return originalValue;}
            if (currentTime==duration) {return originalValue+alteration;}
            if (!cycle) {cycle=duration*0.3;}
            var s;
            if (!extent || extent< Math.abs(alteration)) {
                extent=alteration;
                s =cycle/4;
            } else {s=cycle/(Math.PI*2)*Math.asin(alteration/extent);}
            return originalValue+alteration+extent*Math.pow(2,-currentTime/duration*10)*Math.sin((currentTime-s)*(2*Math.PI)/cycle);
        },
        easeInOut:function (originalValue,alteration,currentTime,duration,extent,cycle) {
            if (!currentTime) {return originalValue;}
            if (currentTime==duration) {return originalValue+alteration;}
            if (!cycle) {cycle=duration*0.45;}
            var s;
            if (!extent || extent< Math.abs(alteration)) {
                extent=alteration;
                s =cycle/4;
            } else {s=cycle/(Math.PI*2)*Math.asin(alteration/extent);}
            var progress = currentTime/duration*2;
            if (progress<1) {
                return originalValue-0.5*extent*Math.pow(2,10*(progress-=1))*Math.sin( (progress*duration-s)*(2*Math.PI)/cycle);
            } else {
                return originalValue+alteration+0.5*extent*Math.pow(2,-10*(progress-=1)) * Math.sin( (progress*duration-s)*(2*Math.PI)/cycle);
            }
        }
    },
    back:{
        easeIn: function (originalValue,alteration,currentTime,duration,s){
            if (typeof s == "undefined") {s = 1.70158;}
            return originalValue+alteration*(currentTime/=duration)*currentTime*((s+1)*currentTime - s);
        },
        easeOut: function (originalValue,alteration,currentTime,duration,s) {
            if (typeof s == "undefined") {s = 1.70158;}
            return originalValue+alteration*((currentTime=currentTime/duration-1)*currentTime*((s+1)*currentTime + s) + 1);
        },
        easeInOut: function (originalValue,alteration,currentTime,duration,s){
            if (typeof s == "undefined") {s = 1.70158;}
            if ((currentTime/=duration/2) < 1) {
                return originalValue+alteration/2*(Math.pow(currentTime,2)*(((s*=(1.525))+1)*currentTime- s));
            }
            return originalValue+alteration/2*((currentTime-=2)*currentTime*(((s*=(1.525))+1)*currentTime+ s)+2);
        }
    },
    bounce:{
        easeIn: function(originalValue,alteration,currentTime,duration){
            return originalValue+alteration-Tween.Bounce.easeOut(0,alteration,duration-currentTime,duration);
        },
        easeOut: function(originalValue,alteration,currentTime,duration){
            if ((currentTime/=duration) < (1/2.75)) {
                return alteration*(7.5625*Math.pow(currentTime,2))+originalValue;
            } else if (currentTime < (2/2.75)) {
                return alteration*(7.5625*(currentTime-=(1.5/2.75))*currentTime + .75)+originalValue;
            } else if (currentTime< (2.5/2.75)) {
                return alteration*(7.5625*(currentTime-=(2.25/2.75))*currentTime + .9375)+originalValue;
            } else {
                return alteration*(7.5625*(currentTime-=(2.625/2.75))*currentTime + .984375)+originalValue;
            }
        },
        easeInOut: function (originalValue,alteration,currentTime,duration){
            if (currentTime< duration/2) {
                return Tween.Bounce.easeIn(0,alteration,currentTime*2,duration) *0.5+originalValue;
            } else {
                return Tween.Bounce.easeOut(0,alteration,currentTime*2-duration,duration) *0.5 + alteration*0.5 +originalValue;
            }
        }
    }
};