react-native/Libraries/Utilities/DevSettings.js

/**
 * Copyright (c) Facebook, Inc. and its affiliates.
 *
 * @format
 */

import NativeDevSettings from '../NativeModules/specs/NativeDevSettings';
import NativeEventEmitter from '../EventEmitter/NativeEventEmitter';

class DevSettings extends NativeEventEmitter {
  _menuItems: Map<string, () => mixed>;

  constructor() {
    super(NativeDevSettings);

    this._menuItems = new Map();
  }

  addMenuItem(title: string, handler: () => mixed) {
    // Make sure items are not added multiple times. This can
    // happen when hot reloading the module that registers the
    // menu items. The title is used as the id which means we
    // don't support multiple items with the same name.
    const oldHandler = this._menuItems.get(title);
    if (oldHandler != null) {
      this.removeListener('didPressMenuItem', oldHandler);
    } else {
      NativeDevSettings.addMenuItem(title);
    }

    this._menuItems.set(title, handler);
    this.addListener('didPressMenuItem', event => {
      if (event.title === title) {
        handler();
      }
    });
  }

  reload() {
    NativeDevSettings.reload();
  }

  // TODO: Add other dev setting methods exposed by the native module.
}

// Avoid including the full `NativeDevSettings` class in prod.
class NoopDevSettings {
  addMenuItem(title: string, handler: () => mixed) {}
  reload() {}
}

module.exports = __DEV__ ? new DevSettings() : new NoopDevSettings();