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/**
 * Get the closest matching element up the DOM tree.
 * @private
 * @param  {Element} elem     Starting element
 * @param  {String}  selector Selector to match against
 * @return {Boolean|Element}  Returns null if not match found
 */
var getClosest = function ( elem, selector ) {

	// Element.matches() polyfill
	if (!Element.prototype.matches) {
		Element.prototype.matches =
			Element.prototype.matchesSelector ||
			Element.prototype.mozMatchesSelector ||
			Element.prototype.msMatchesSelector ||
			Element.prototype.oMatchesSelector ||
			Element.prototype.webkitMatchesSelector ||
			function(s) {
				var matches = (this.document || this.ownerDocument).querySelectorAll(s),
					i = matches.length;
				while (--i >= 0 && matches.item(i) !== this) {}
				return i > -1;
			};
	}

	// Get closest match
	for ( ; elem && elem !== document; elem = elem.parentNode ) {
		if ( elem.matches( selector ) ) return elem;
	}

	return null;

};