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wp-includes/js/dist/vendor/wp-polyfill-element-closest.js

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+// element-closest | CC0-1.0 | github.com/jonathantneal/closest
+
+(function (ElementProto) {
+	if (typeof ElementProto.matches !== 'function') {
+		ElementProto.matches = ElementProto.msMatchesSelector || ElementProto.mozMatchesSelector || ElementProto.webkitMatchesSelector || function matches(selector) {
+			var element = this;
+			var elements = (element.document || element.ownerDocument).querySelectorAll(selector);
+			var index = 0;
+
+			while (elements[index] && elements[index] !== element) {
+				++index;
+			}
+
+			return Boolean(elements[index]);
+		};
+	}
+
+	if (typeof ElementProto.closest !== 'function') {
+		ElementProto.closest = function closest(selector) {
+			var element = this;
+
+			while (element && element.nodeType === 1) {
+				if (element.matches(selector)) {
+					return element;
+				}
+
+				element = element.parentNode;
+			}
+
+			return null;
+		};
+	}
+})(window.Element.prototype);