ionic-framework/scripts/polyfill/polyfill.dom.js

(function(){
  "use strict";

  if (typeof Element.prototype.matches !== 'function') {
    Element.prototype.matches = Element.prototype.msMatchesSelector || Element.prototype.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 Element.prototype.closest !== 'function') {
    Element.prototype.closest = function closest(selector) {
      var element = this;
      while (element && element.nodeType === 1) {
        if (element.matches(selector)) {
          return element;
        }
        element = element.parentNode;
      }
      return null;
    };
  }

})();