js缓动函数

公式一：

var Tween = {
    Linear: function(t, b, c, d) {
        return c * t / 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 / 2 * t * t + b;
            return - c / 2 * ((--t) * (t - 2) - 1) + b;
        }
    },
    Cubic: {
        easeIn: function(t, b, c, d) {
            return c * (t /= d) * t * t + b;
        },
        easeOut: function(t, b, c, d) {
            return c * ((t = t / d - 1) * t * t + 1) + b;
        },
        easeInOut: 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;
        }
    },
    Quart: {
        easeIn: function(t, b, c, d) {
            return c * (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) return c / 2 * t * t * t * t + b;
            return - c / 2 * ((t -= 2) * t * t * t - 2) + b;
        }
    },
    Quint: {
        easeIn: function(t, b, c, d) {
            return c * (t /= d) * t * t * t * t + b;
        },
        easeOut: function(t, b, c, d) {
            return c * ((t = t / d - 1) * t * t * t * t + 1) + b;
        },
        easeInOut: 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;
        }
    },
    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.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) 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 - t * t) - 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 / (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) {
            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);
        },
        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 * (.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;
        }
    },
    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 * (t * t * (((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 * (7.5625 * 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;
            }
        },
        easeInOut: function(t, b, c, d) {
            if (t < d / 2) return Tween.Bounce.easeIn(t * 2, 0, c, d) * .5 + b;
            else return Tween.Bounce.easeOut(t * 2 - d, 0, c, d) * .5 + c * .5 + b;
        }
    }
}
公式二：

var tween = {
    easeInQuad: function(pos) {
        return Math.pow(pos, 2);
    },
    easeOutQuad: function(pos) {
        return - (Math.pow((pos - 1), 2) - 1);
    },
    easeInOutQuad: function(pos) {
        if ((pos /= 0.5) < 1) return 0.5 * Math.pow(pos, 2);
        return - 0.5 * ((pos -= 2) * pos - 2);
    },
    easeInCubic: function(pos) {
        return Math.pow(pos, 3);
    },
    easeOutCubic: function(pos) {
        return (Math.pow((pos - 1), 3) + 1);
    },
    easeInOutCubic: function(pos) {
        if ((pos /= 0.5) < 1) return 0.5 * Math.pow(pos, 3);
        return 0.5 * (Math.pow((pos - 2), 3) + 2);
    },
    easeInQuart: function(pos) {
        return Math.pow(pos, 4);
    },
    easeOutQuart: function(pos) {
        return - (Math.pow((pos - 1), 4) - 1)
    },
    easeInOutQuart: function(pos) {
        if ((pos /= 0.5) < 1) return 0.5 * Math.pow(pos, 4);
        return - 0.5 * ((pos -= 2) * Math.pow(pos, 3) - 2);
    },
    easeInQuint: function(pos) {
        return Math.pow(pos, 5);
    },
    easeOutQuint: function(pos) {
        return (Math.pow((pos - 1), 5) + 1);
    },
    easeInOutQuint: function(pos) {
        if ((pos /= 0.5) < 1) return 0.5 * Math.pow(pos, 5);
        return 0.5 * (Math.pow((pos - 2), 5) + 2);
    },
    easeInSine: function(pos) {
        return - Math.cos(pos * (Math.PI / 2)) + 1;
    },
    easeOutSine: function(pos) {
        return Math.sin(pos * (Math.PI / 2));
    },
    easeInOutSine: function(pos) {
        return ( - .5 * (Math.cos(Math.PI * pos) - 1));
    },
    easeInExpo: function(pos) {
        return (pos == 0) ? 0 : Math.pow(2, 10 * (pos - 1));
    },
    easeOutExpo: function(pos) {
        return (pos == 1) ? 1 : -Math.pow(2, -10 * pos) + 1;
    },
    easeInOutExpo: function(pos) {
        if (pos == 0) return 0;
        if (pos == 1) return 1;
        if ((pos /= 0.5) < 1) return 0.5 * Math.pow(2, 10 * (pos - 1));
        return 0.5 * ( - Math.pow(2, -10 * --pos) + 2);
    },
    easeInCirc: function(pos) {
        return - (Math.sqrt(1 - (pos * pos)) - 1);
    },
    easeOutCirc: function(pos) {
        return Math.sqrt(1 - Math.pow((pos - 1), 2))
    },
    easeInOutCirc: function(pos) {
        if ((pos /= 0.5) < 1) return - 0.5 * (Math.sqrt(1 - pos * pos) - 1);
        return 0.5 * (Math.sqrt(1 - (pos -= 2) * pos) + 1);
    },
    easeOutBounce: function(pos) {
        if ((pos) < (1 / 2.75)) {
            return (7.5625 * pos * pos);
        } else if (pos < (2 / 2.75)) {
            return (7.5625 * (pos -= (1.5 / 2.75)) * pos + .75);
        } else if (pos < (2.5 / 2.75)) {
            return (7.5625 * (pos -= (2.25 / 2.75)) * pos + .9375);
        } else {
            return (7.5625 * (pos -= (2.625 / 2.75)) * pos + .984375);
        }
    },
    easeInBack: function(pos) {
        var s = 1.70158;
        return (pos) * pos * ((s + 1) * pos - s);
    },
    easeOutBack: function(pos) {
        var s = 1.70158;
        return (pos = pos - 1) * pos * ((s + 1) * pos + s) + 1;
    },
    easeInOutBack: function(pos) {
        var s = 1.70158;
        if ((pos /= 0.5) < 1) return 0.5 * (pos * pos * (((s *= (1.525)) + 1) * pos - s));
        return 0.5 * ((pos -= 2) * pos * (((s *= (1.525)) + 1) * pos + s) + 2);
    },
    elastic: function(pos) {
        return - 1 * Math.pow(4, -8 * pos) * Math.sin((pos * 6 - 1) * (2 * Math.PI) / 2) + 1;
    },
    swingFromTo: function(pos) {
        var s = 1.70158;
        return ((pos /= 0.5) < 1) ? 0.5 * (pos * pos * (((s *= (1.525)) + 1) * pos - s)) : 0.5 * ((pos -= 2) * pos * (((s *= (1.525)) + 1) * pos + s) + 2);
    },
    swingFrom: function(pos) {
        var s = 1.70158;
        return pos * pos * ((s + 1) * pos - s);
    },
    swingTo: function(pos) {
        var s = 1.70158;
        return (pos -= 1) * pos * ((s + 1) * pos + s) + 1;
    },
    bounce: function(pos) {
        if (pos < (1 / 2.75)) {
            return (7.5625 * pos * pos);
        } else if (pos < (2 / 2.75)) {
            return (7.5625 * (pos -= (1.5 / 2.75)) * pos + .75);
        } else if (pos < (2.5 / 2.75)) {
            return (7.5625 * (pos -= (2.25 / 2.75)) * pos + .9375);
        } else {
            return (7.5625 * (pos -= (2.625 / 2.75)) * pos + .984375);
        }
    },
    bouncePast: function(pos) {
        if (pos < (1 / 2.75)) {
            return (7.5625 * pos * pos);
        } else if (pos < (2 / 2.75)) {
            return 2 - (7.5625 * (pos -= (1.5 / 2.75)) * pos + .75);
        } else if (pos < (2.5 / 2.75)) {
            return 2 - (7.5625 * (pos -= (2.25 / 2.75)) * pos + .9375);
        } else {
            return 2 - (7.5625 * (pos -= (2.625 / 2.75)) * pos + .984375);
        }
    },
    easeFromTo: function(pos) {
        if ((pos /= 0.5) < 1) return 0.5 * Math.pow(pos, 4);
        return - 0.5 * ((pos -= 2) * Math.pow(pos, 3) - 2);
    },
    easeFrom: function(pos) {
        return Math.pow(pos, 4);
    },
    easeTo: function(pos) {
        return Math.pow(pos, 0.25);
    },
    linear: function(pos) {
        return pos
    },
    sinusoidal: function(pos) {
        return ( - Math.cos(pos * Math.PI) / 2) + 0.5;
    },
    reverse: function(pos) {
        return 1 - pos;
    },
    mirror: function(pos, transition) {
        transition = transition || tween.sinusoidal;
        if (pos < 0.5) return transition(pos * 2);
        else return transition(1 - (pos - 0.5) * 2);
    },
    flicker: function(pos) {
        var pos = pos + (Math.random() - 0.5) / 5;
        return tween.sinusoidal(pos < 0 ? 0 : pos > 1 ? 1 : pos);
    },
    wobble: function(pos) {
        return ( - Math.cos(pos * Math.PI * (9 * pos)) / 2) + 0.5;
    },
    pulse: function(pos, pulses) {
        return ( - Math.cos((pos * ((pulses || 5) - .5) * 2) * Math.PI) / 2) + .5;
    },
    blink: function(pos, blinks) {
        return Math.round(pos * (blinks || 5)) % 2;
    },
    spring: function(pos) {
        return 1 - (Math.cos(pos * 4.5 * Math.PI) * Math.exp( - pos * 6));
    },
    none: function(pos) {
        return 0
    },
    full: function(pos) {
        return 1
    }
}

转自：http://www.cnblogs.com/sky000/archive/2010/10/14/1851274.html