(function (global, factory) {

  typeof exports === 'object' && typeof module !== 'undefined' ? factory() :

  typeof define === 'function' && define.amd ? define('inert', factory) :

  (factory());

}(this, (function () { 'use strict';

  var _createClass = function () { function defineProperties(target, props) { for (var i = 0; i < props.length; i++) { var descriptor = props[i]; descriptor.enumerable = descriptor.enumerable || false; descriptor.configurable = true; if ("value" in descriptor) descriptor.writable = true; Object.defineProperty(target, descriptor.key, descriptor); } } return function (Constructor, protoProps, staticProps) { if (protoProps) defineProperties(Constructor.prototype, protoProps); if (staticProps) defineProperties(Constructor, staticProps); return Constructor; }; }();

  function _classCallCheck(instance, Constructor) { if (!(instance instanceof Constructor)) { throw new TypeError("Cannot call a class as a function"); } }

  /**

   * This work is licensed under the W3C Software and Document License

   * (http://www.w3.org/Consortium/Legal/2015/copyright-software-and-document).

   */

  (function () {

    // Return early if we're not running inside of the browser.

    if (typeof window === 'undefined' || typeof Element === 'undefined') {

      return;

    }

    // Convenience function for converting NodeLists.

    /** @type {typeof Array.prototype.slice} */

    var slice = Array.prototype.slice;

    /**

     * IE has a non-standard name for "matches".

     * @type {typeof Element.prototype.matches}

     */

    var matches = Element.prototype.matches || Element.prototype.msMatchesSelector;

    /** @type {string} */

    var _focusableElementsString = ['a[href]', 'area[href]', 'input:not([disabled])', 'select:not([disabled])', 'textarea:not([disabled])', 'button:not([disabled])', 'details', 'summary', 'iframe', 'object', 'embed', 'video', '[contenteditable]'].join(',');

    /**

     * `InertRoot` manages a single inert subtree, i.e. a DOM subtree whose root element has an `inert`

     * attribute.

     *

     * Its main functions are:

     *

     * - to create and maintain a set of managed `InertNode`s, including when mutations occur in the

     *   subtree. The `makeSubtreeUnfocusable()` method handles collecting `InertNode`s via registering

     *   each focusable node in the subtree with the singleton `InertManager` which manages all known

     *   focusable nodes within inert subtrees. `InertManager` ensures that a single `InertNode`

     *   instance exists for each focusable node which has at least one inert root as an ancestor.

     *

     * - to notify all managed `InertNode`s when this subtree stops being inert (i.e. when the `inert`

     *   attribute is removed from the root node). This is handled in the destructor, which calls the

     *   `deregister` method on `InertManager` for each managed inert node.

     */

    var InertRoot = function () {

      /**

       * @param {!HTMLElement} rootElement The HTMLElement at the root of the inert subtree.

       * @param {!InertManager} inertManager The global singleton InertManager object.

       */

      function InertRoot(rootElement, inertManager) {

        _classCallCheck(this, InertRoot);

        /** @type {!InertManager} */

        this._inertManager = inertManager;

        /** @type {!HTMLElement} */

        this._rootElement = rootElement;

        /**

         * @type {!Set<!InertNode>}

         * All managed focusable nodes in this InertRoot's subtree.

         */

        this._managedNodes = new Set();

        // Make the subtree hidden from assistive technology

        if (this._rootElement.hasAttribute('aria-hidden')) {

          /** @type {?string} */

          this._savedAriaHidden = this._rootElement.getAttribute('aria-hidden');

        } else {

          this._savedAriaHidden = null;

        }

        this._rootElement.setAttribute('aria-hidden', 'true');

        // Make all focusable elements in the subtree unfocusable and add them to _managedNodes

        this._makeSubtreeUnfocusable(this._rootElement);

        // Watch for:

        // - any additions in the subtree: make them unfocusable too

        // - any removals from the subtree: remove them from this inert root's managed nodes

        // - attribute changes: if `tabindex` is added, or removed from an intrinsically focusable

        //   element, make that node a managed node.

        this._observer = new MutationObserver(this._onMutation.bind(this));

        this._observer.observe(this._rootElement, { attributes: true, childList: true, subtree: true });

      }

      /**

       * Call this whenever this object is about to become obsolete.  This unwinds all of the state

       * stored in this object and updates the state of all of the managed nodes.

       */

      _createClass(InertRoot, [{

        key: 'destructor',

        value: function destructor() {

          this._observer.disconnect();

          if (this._rootElement) {

            if (this._savedAriaHidden !== null) {

              this._rootElement.setAttribute('aria-hidden', this._savedAriaHidden);

            } else {

              this._rootElement.removeAttribute('aria-hidden');

            }

          }

          this._managedNodes.forEach(function (inertNode) {

            this._unmanageNode(inertNode.node);

          }, this);

          // Note we cast the nulls to the ANY type here because:

          // 1) We want the class properties to be declared as non-null, or else we

          //    need even more casts throughout this code. All bets are off if an

          //    instance has been destroyed and a method is called.

          // 2) We don't want to cast "this", because we want type-aware optimizations

          //    to know which properties we're setting.

          this._observer = /** @type {?} */null;

          this._rootElement = /** @type {?} */null;

          this._managedNodes = /** @type {?} */null;

          this._inertManager = /** @type {?} */null;

        }

        /**

         * @return {!Set<!InertNode>} A copy of this InertRoot's managed nodes set.

         */

      }, {

        key: '_makeSubtreeUnfocusable',

        /**

         * @param {!Node} startNode

         */

        value: function _makeSubtreeUnfocusable(startNode) {

          var _this2 = this;

          composedTreeWalk(startNode, function (node) {

            return _this2._visitNode(node);

          });

          var activeElement = document.activeElement;

          if (!document.body.contains(startNode)) {

            // startNode may be in shadow DOM, so find its nearest shadowRoot to get the activeElement.

            var node = startNode;

            /** @type {!ShadowRoot|undefined} */

            var root = undefined;

            while (node) {

              if (node.nodeType === Node.DOCUMENT_FRAGMENT_NODE) {

                root = /** @type {!ShadowRoot} */node;

                break;

              }

              node = node.parentNode;

            }

            if (root) {

              activeElement = root.activeElement;

            }

          }

          if (startNode.contains(activeElement)) {

            activeElement.blur();

            // In IE11, if an element is already focused, and then set to tabindex=-1

            // calling blur() will not actually move the focus.

            // To work around this we call focus() on the body instead.

            if (activeElement === document.activeElement) {

              document.body.focus();

            }

          }

        }

        /**

         * @param {!Node} node

         */

      }, {

        key: '_visitNode',

        value: function _visitNode(node) {

          if (node.nodeType !== Node.ELEMENT_NODE) {

            return;

          }

          var element = /** @type {!HTMLElement} */node;

          // If a descendant inert root becomes un-inert, its descendants will still be inert because of

          // this inert root, so all of its managed nodes need to be adopted by this InertRoot.

          if (element !== this._rootElement && element.hasAttribute('inert')) {

            this._adoptInertRoot(element);

          }

          if (matches.call(element, _focusableElementsString) || element.hasAttribute('tabindex')) {

            this._manageNode(element);

          }

        }

        /**

         * Register the given node with this InertRoot and with InertManager.

         * @param {!Node} node

         */

      }, {

        key: '_manageNode',

        value: function _manageNode(node) {

          var inertNode = this._inertManager.register(node, this);

          this._managedNodes.add(inertNode);

        }

        /**

         * Unregister the given node with this InertRoot and with InertManager.

         * @param {!Node} node

         */

      }, {

        key: '_unmanageNode',

        value: function _unmanageNode(node) {

          var inertNode = this._inertManager.deregister(node, this);

          if (inertNode) {

            this._managedNodes['delete'](inertNode);

          }

        }

        /**

         * Unregister the entire subtree starting at `startNode`.

         * @param {!Node} startNode

         */

      }, {

        key: '_unmanageSubtree',

        value: function _unmanageSubtree(startNode) {

          var _this3 = this;

          composedTreeWalk(startNode, function (node) {

            return _this3._unmanageNode(node);

          });

        }

        /**

         * If a descendant node is found with an `inert` attribute, adopt its managed nodes.

         * @param {!HTMLElement} node

         */

      }, {

        key: '_adoptInertRoot',

        value: function _adoptInertRoot(node) {

          var inertSubroot = this._inertManager.getInertRoot(node);

          // During initialisation this inert root may not have been registered yet,

          // so register it now if need be.

          if (!inertSubroot) {

            this._inertManager.setInert(node, true);

            inertSubroot = this._inertManager.getInertRoot(node);

          }

          inertSubroot.managedNodes.forEach(function (savedInertNode) {

            this._manageNode(savedInertNode.node);

          }, this);

        }

        /**

         * Callback used when mutation observer detects subtree additions, removals, or attribute changes.

         * @param {!Array<!MutationRecord>} records

         * @param {!MutationObserver} self

         */

      }, {

        key: '_onMutation',

        value: function _onMutation(records, self) {

          records.forEach(function (record) {

            var target = /** @type {!HTMLElement} */record.target;

            if (record.type === 'childList') {

              // Manage added nodes

              slice.call(record.addedNodes).forEach(function (node) {

                this._makeSubtreeUnfocusable(node);

              }, this);

              // Un-manage removed nodes

              slice.call(record.removedNodes).forEach(function (node) {

                this._unmanageSubtree(node);

              }, this);

            } else if (record.type === 'attributes') {

              if (record.attributeName === 'tabindex') {

                // Re-initialise inert node if tabindex changes

                this._manageNode(target);

              } else if (target !== this._rootElement && record.attributeName === 'inert' && target.hasAttribute('inert')) {

                // If a new inert root is added, adopt its managed nodes and make sure it knows about the

                // already managed nodes from this inert subroot.

                this._adoptInertRoot(target);

                var inertSubroot = this._inertManager.getInertRoot(target);

                this._managedNodes.forEach(function (managedNode) {

                  if (target.contains(managedNode.node)) {

                    inertSubroot._manageNode(managedNode.node);

                  }

                });

              }

            }

          }, this);

        }

      }, {

        key: 'managedNodes',

        get: function get() {

          return new Set(this._managedNodes);

        }

        /** @return {boolean} */

      }, {

        key: 'hasSavedAriaHidden',

        get: function get() {

          return this._savedAriaHidden !== null;

        }

        /** @param {?string} ariaHidden */

      }, {

        key: 'savedAriaHidden',

        set: function set(ariaHidden) {

          this._savedAriaHidden = ariaHidden;

        }

        /** @return {?string} */

        ,

        get: function get() {

          return this._savedAriaHidden;

        }

      }]);

      return InertRoot;

    }();

    /**

     * `InertNode` initialises and manages a single inert node.

     * A node is inert if it is a descendant of one or more inert root elements.

     *

     * On construction, `InertNode` saves the existing `tabindex` value for the node, if any, and

     * either removes the `tabindex` attribute or sets it to `-1`, depending on whether the element

     * is intrinsically focusable or not.

     *

     * `InertNode` maintains a set of `InertRoot`s which are descendants of this `InertNode`. When an

     * `InertRoot` is destroyed, and calls `InertManager.deregister()`, the `InertManager` notifies the

     * `InertNode` via `removeInertRoot()`, which in turn destroys the `InertNode` if no `InertRoot`s

     * remain in the set. On destruction, `InertNode` reinstates the stored `tabindex` if one exists,

     * or removes the `tabindex` attribute if the element is intrinsically focusable.

     */

    var InertNode = function () {

      /**

       * @param {!Node} node A focusable element to be made inert.

       * @param {!InertRoot} inertRoot The inert root element associated with this inert node.

       */

      function InertNode(node, inertRoot) {

        _classCallCheck(this, InertNode);

        /** @type {!Node} */

        this._node = node;

        /** @type {boolean} */

        this._overrodeFocusMethod = false;

        /**

         * @type {!Set<!InertRoot>} The set of descendant inert roots.

         *    If and only if this set becomes empty, this node is no longer inert.

         */

        this._inertRoots = new Set([inertRoot]);

        /** @type {?number} */

        this._savedTabIndex = null;

        /** @type {boolean} */

        this._destroyed = false;

        // Save any prior tabindex info and make this node untabbable

        this.ensureUntabbable();

      }

      /**

       * Call this whenever this object is about to become obsolete.

       * This makes the managed node focusable again and deletes all of the previously stored state.

       */

      _createClass(InertNode, [{

        key: 'destructor',

        value: function destructor() {

          this._throwIfDestroyed();

          if (this._node && this._node.nodeType === Node.ELEMENT_NODE) {