WordPress/wp-content/themes/twentytwentyone/assets/js/polyfills.js

/**
 * File primary-navigation.js.
 *
 * Required to open and close the mobile navigation.
 */

/**
 * Polyfill for Element.closest() because we need to support IE11.
 *
 * @see https://developer.mozilla.org/en-US/docs/Web/API/Element/closest
 */
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 ( Element.prototype.matches.call( el, s ) ) {
				return el;
			}
			el = el.parentElement || el.parentNode;
		} while ( el !== null && el.nodeType === 1 );
		return null;
	};
}

/**
 * Polyfill for NodeList.foreach() because we need to support IE11.
 *
 * @see https://developer.mozilla.org/en-US/docs/Web/API/NodeList/forEach
 */
if ( window.NodeList && ! NodeList.prototype.forEach ) {
	NodeList.prototype.forEach = function( callback, thisArg ) {
		var i;
		thisArg = thisArg || window;
		for ( i = 0; i < this.length; i++ ) {
			callback.call( thisArg, this[i], i, this );
		}
	};
}