// https://developer.mozilla.org/en-US/docs/Web/API/Element/closest#Polyfill
if (!Element.prototype.matches) {
    Element.prototype.matches = Element.prototype.msMatchesSelector || Element.prototype.webkitMatchesSelector;
}

if (!Element.prototype.closest) {
    Element.prototype.closest = function(s) {
        var el = this;

        do {
            if (el.matches(s)) return el;
            el = el.parentElement || el.parentNode;
        } while (el !== null && el.nodeType === 1);

        return null;
    };
}