closest.js

Element.prototype.closest = function(selector)
    {
        var element = this;

        do if (element.matches(selector)) return element;
        while (element = element.parentElement);

        return null;
    };
    
Element.prototype.matches = (function($)
    {
        return $.matchesSelector
            || $.webkitMatchesSelector
            || $.mozMatchesSelector
            || $.msMatchesSelector
            || $.oMatchesSelector;
    })(Element.prototype);