Easing functions allow you to apply non-linear motion to effects. 当你运用move或resize等效果的时候,有时候会很死板。因为它的运动轨迹是直线的,而如果要运动轨迹是非线性的话,就可以尝试use easing functions.
example: http://www.jamesward.com/easingFunctionFun/easingFunctionFun.html .
also you can get source here: http://www.jamesward.com/easingFunctionFun/srcview/index.html