ES5 polyfill (for IE/Edge)

if (!Element.prototype.matches) Element.prototype.matches = Element.prototype.msMatchesSelector;
if (!Element.prototype.closest) Element.prototype.closest = function(selector) {
    var el = this;
    while (el) {
        if (el.matches(selector)) {
            return el;
        }
        el = el.parentElement;
    }
};


Array.prototype.last = function() {
    return this[this.length - 1];
    // undefined is returned for array[-1]
}

Array.prototype.first = function() {
    return this[0];
}


NodeList.prototype.forEach = NodeList.prototype.forEach || Array.prototype.forEach;
NodeList.prototype.last = NodeList.prototype.last || Array.prototype.last;
NodeList.prototype.first = NodeList.prototype.first || Array.prototype.first;
NodeList.prototype.lastIndexOf = NodeList.prototype.lastIndexOf || Array.prototype.lastIndexOf;
NodeList.prototype.indexOf = NodeList.prototype.indexOf || Array.prototype.indexOf;
NodeList.prototype.some = NodeList.prototype.some || Array.prototype.some;
NodeList.prototype.every = NodeList.prototype.every || Array.prototype.every;