一起开始的旅程.

在KISSY1.2中有16中中缓动函数。

先解释什么叫缓动函数。这个的从物理的角度描述了。

我们都知道自由落体运动，理想情况下，自由落体就是一个速度不断加快的运动。

用函数表示就Y=kX²

所有感觉很舒服的动画总会或多或少的使用各种缓动效果

Robert Penner 博士的缓动函数介绍

使用缓动之后的动画会让人感觉很自然.

KISSY中的缓动函数定义在srcanimeasing.js

/**
             * Uniform speed between points.
             */
            easeNone: function (t) {
                return t;
            },

            /**
             * Begins slowly and accelerates towards end. (quadratic)
             */
            easeIn: function (t) {
                return t * t;
            },

            /**
             * Begins quickly and decelerates towards end.  (quadratic)
             */
            easeOut: function (t) {
                return ( 2 - t) * t;
            },

            /**
             * Begins slowly and decelerates towards end. (quadratic)
             */
            easeBoth: function (t) {
                return (t *= 2) < 1 ?
                    .5 * t * t :
                    .5 * (1 - (--t) * (t - 2));
            },

            /**
             * Begins slowly and accelerates towards end. (quartic)
             */
            easeInStrong: function (t) {
                return t * t * t * t;
            },

            /**
             * Begins quickly and decelerates towards end.  (quartic)
             */
            easeOutStrong: function (t) {
                return 1 - (--t) * t * t * t;
            },

            /**
             * Begins slowly and decelerates towards end. (quartic)
             */
            easeBothStrong: function (t) {
                return (t *= 2) < 1 ?
                    .5 * t * t * t * t :
                    .5 * (2 - (t -= 2) * t * t * t);
            },

            /**
             * Snap in elastic effect.
             */

            elasticIn: function (t) {
                var p = .3, s = p / 4;
                if (t === 0 || t === 1) return t;
                return -(pow(2, 10 * (t -= 1)) * sin((t - s) * (2 * PI) / p));
            },

            /**
             * Snap out elastic effect.
             */
            elasticOut: function (t) {
                var p = .3, s = p / 4;
                if (t === 0 || t === 1) return t;
                return pow(2, -10 * t) * sin((t - s) * (2 * PI) / p) + 1;
            },

            /**
             * Snap both elastic effect.
             */
            elasticBoth: function (t) {
                var p = .45, s = p / 4;
                if (t === 0 || (t *= 2) === 2) return t;

                if (t < 1) {
                    return -.5 * (pow(2, 10 * (t -= 1)) *
                        sin((t - s) * (2 * PI) / p));
                }
                return pow(2, -10 * (t -= 1)) *
                    sin((t - s) * (2 * PI) / p) * .5 + 1;
            },

            /**
             * Backtracks slightly, then reverses direction and moves to end.
             */
            backIn: function (t) {
                if (t === 1) t -= .001;
                return t * t * ((BACK_CONST + 1) * t - BACK_CONST);
            },

            /**
             * Overshoots end, then reverses and comes back to end.
             */
            backOut: function (t) {
                return (t -= 1) * t * ((BACK_CONST + 1) * t + BACK_CONST) + 1;
            },

            /**
             * Backtracks slightly, then reverses direction, overshoots end,
             * then reverses and comes back to end.
             */
            backBoth: function (t) {
                if ((t *= 2 ) < 1) {
                    return .5 * (t * t * (((BACK_CONST *= (1.525)) + 1) * t - BACK_CONST));
                }
                return .5 * ((t -= 2) * t * (((BACK_CONST *= (1.525)) + 1) * t + BACK_CONST) + 2);
            },

            /**
             * Bounce off of start.
             */
            bounceIn: function (t) {
                return 1 - Easing.bounceOut(1 - t);
            },

            /**
             * Bounces off end.
             */
            bounceOut: function (t) {
                var s = 7.5625, r;

                if (t < (1 / 2.75)) {
                    r = s * t * t;
                }
                else if (t < (2 / 2.75)) {
                    r = s * (t -= (1.5 / 2.75)) * t + .75;
                }
                else if (t < (2.5 / 2.75)) {
                    r = s * (t -= (2.25 / 2.75)) * t + .9375;
                }
                else {
                    r = s * (t -= (2.625 / 2.75)) * t + .984375;
                }

                return r;
            },

            /**
             * Bounces off start and end.
             */
            bounceBoth: function (t) {
                if (t < .5) {
                    return Easing.bounceIn(t * 2) * .5;
                }
                return Easing.bounceOut(t * 2 - 1) * .5 + .5;
            }

基本上KISSY已经把所有我们可能用的到的缓动函数都已经写好了.