getActiveElement.js.flow

/**
 * Copyright (c) 2013-present, Facebook, Inc.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 *
 * @providesModule getActiveElement
 * @typechecks
 */

/* eslint-disable fb-www/typeof-undefined */

/**
 * Same as document.activeElement but wraps in a try-catch block. In IE it is
 * not safe to call document.activeElement if there is nothing focused.
 *
 * The activeElement will be null only if the document or document body is not
 * yet defined.
 *
 * @param {?DOMDocument} doc Defaults to current document.
 * @return {?DOMElement}
 */
function getActiveElement(doc)
/*?DOMElement*/
{
  doc = doc || (typeof document !== 'undefined' ? document : undefined);

  if (typeof doc === 'undefined') {
    return null;
  }

  try {
    return doc.activeElement || doc.body;
  } catch (e) {
    return doc.body;
  }
}

module.exports = getActiveElement;