file author : 王佳欣
 *  email export let getTransitionEvent = ( ) => { let el = document . createElement ( 'fake_a_element' ) ; let transitions = { 'transition' : 'transitionend' , 'OTransition' : 'oTransitionEnd' , 'MozTransition' : 'transitionend' , 'WebkitTransition' : 'webkitTransitionEnd' } ; for ( let transition in transitions ) { if ( el . style [ transition ] !== undefined ) { getTransitionEvent = ( ) => { return transitions [ transition ] ; } ; return transitions [ transition ] ; } } } ; export let getAnimationEvent = ( ) => { let el = document . createElement ( 'fake_a_element' ) ; let animations = { 'animation' : 'animationend' , 'OAnimation' : 'oAnimationEnd' , 'MozAnimation' : 'animationend' , 'WebkitAnimation' : 'webkitAnimationEnd' } ; for ( let animation in animations ) { if ( el . style [ animation ] !== undefined ) { getAnimationEvent = ( ) => { return animations [ animation ] ; } ; return animations [ animation ] ; } } } ;