ReactErrorUtils.js

/**
 * Copyright 2013-present, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 *
 * @providesModule ReactErrorUtils
 * @flow
 */

'use strict';

var caughtError = null;

/**
 * Call a function while guarding against errors that happens within it.
 *
 * @param {String} name of the guard to use for logging or debugging
 * @param {Function} func The function to invoke
 * @param {*} a Argument
 */
function invokeGuardedCallback<A>(
  name: string,
  func: (a: A) => void,
  a: A,
): void {
  try {
    func(a);
  } catch (x) {
    if (caughtError === null) {
      caughtError = x;
    }
  }
}

var ReactErrorUtils = {
  invokeGuardedCallback: invokeGuardedCallback,

  /**
   * Invoked by ReactTestUtils.Simulate so that any errors thrown by the event
   * handler are sure to be rethrown by rethrowCaughtError.
   */
  invokeGuardedCallbackWithCatch: invokeGuardedCallback,

  /**
   * During execution of guarded functions we will capture the first error which
   * we will rethrow to be handled by the top level error handler.
   */
  rethrowCaughtError: function() {
    if (caughtError) {
      var error = caughtError;
      caughtError = null;
      throw error;
    }
  },
};

if (__DEV__) {
  /**
   * To help development we can get better devtools integration by simulating a
   * real browser event.
   */
  if (typeof window !== 'undefined' &&
      typeof window.dispatchEvent === 'function' &&
      typeof document !== 'undefined' &&
      typeof document.createEvent === 'function') {
    var fakeNode = document.createElement('react');
    ReactErrorUtils.invokeGuardedCallback = function<A>(
      name: string,
      func: (a: A) => void,
      a: A,
    ): void {
      var boundFunc = function() {
        func(a);
      };
      var evtType = `react-${name}`;
      fakeNode.addEventListener(evtType, boundFunc, false);
      var evt = document.createEvent('Event');
      evt.initEvent(evtType, false, false);
      fakeNode.dispatchEvent(evt);
      fakeNode.removeEventListener(evtType, boundFunc, false);
    };
  }
}

module.exports = ReactErrorUtils;