jquery 内置 easing 只有 linear（默认，匀速直线） 和 swing（也就是 easeOutQuad）。

jquery easing 1.3 31 种（包括 swing）。算上 linear 全部可选的 easing 效果是 32 种。

‘linear’, ‘easeOutQuad’, ‘easeInQuad’, ‘easeOutQuad’, ‘easeInOutQuad’, ‘easeInCubic’, ‘easeOutCubic’, ‘easeInOutCubic’, ‘easeInQuart’, ‘easeOutQuart’, ‘easeInOutQuart’, ‘easeInQuint’, ‘easeOutQuint’, ‘easeInOutQuint’, ‘easeInSine’, ‘easeOutSine’, ‘easeInOutSine’, ‘easeInExpo’, ‘easeOutExpo’, ‘easeInOutExpo’, ‘easeInCirc’, ‘easeOutCirc’, ‘easeInOutCirc’, ‘easeInElastic’, ‘easeOutElastic’, ‘easeInOutElastic’, ‘easeInBack’, ‘easeOutBack’, ‘easeInOutBack’, ‘easeInBounce’, ‘easeOutBounce’, ‘easeInOutBounce’