怎么使用JavaScript检测CSS转换何时结束

function gettransitionend(){

    var root = document.documentElement

    var transitions = {

        'transition':'transitionend',

        'OTransition':'oTransitionEnd',

        'MozTransition':'transitionend',

        'WebkitTransition':'webkitTransitionEnd'

        }

    for (var t in transitions){

        if (root.style[t] !== undefined ){

            return transitions[t];

        }

    }

    return undefined

}

//Example Usage:

var transitionendevt = gettransitionend()

if (transitionendevt){ // if transitionend event supported by browser

    element.addEventListener(transitionendevt, function(e){

        // do something after end of transition

    }, false)

}