Check when the transition is finished

onTransitionEnd.js

/* From Modernizr */
function whichTransitionEvent() {
    var t;
    var el = document.createElement('fakeelement');
    var transitions = {
        'transition': 'transitionend',
        'OTransition': 'oTransitionEnd',
        'MozTransition': 'transitionend',
        'WebkitTransition': 'webkitTransitionEnd'
    }

    for (t in transitions) {
        if (el.style[t] !== undefined) {
            return transitions[t];
        }
    }
}

/* Listen for a transition! */
var transitionEvent = whichTransitionEvent();


const
    onTransitionEnd = function (el, fn) {
        // console.log('entering here...', fn);
        transitionEvent && el.addEventListener(transitionEvent, function() {
            // console.log('done!');
            fn();
        });
    };

export default onTransitionEnd;