expo-updates/src/UpdatesEmitter.ts

Fetches and manages remotely-hosted assets and updates to your app's JS bundle.

import { EventEmitter as NativeEventEmitter } from 'expo-modules-core';
import { EventEmitter as JsEventEmitter } from 'fbemitter';

import ExpoUpdatesModule from './ExpoUpdates';
import { transformNativeStateMachineContext } from './Updates';
import type { UpdatesNativeStateChangeEvent } from './Updates.types';

const _nativeEventEmitter = new NativeEventEmitter(ExpoUpdatesModule);
_nativeEventEmitter.addListener('Expo.nativeUpdatesStateChangeEvent', _emitNativeStateChangeEvent);

let _jsEventEmitter: JsEventEmitter | null = null;
function _getJsEventEmitter(): JsEventEmitter {
  if (!_jsEventEmitter) {
    _jsEventEmitter = new JsEventEmitter();
  }
  return _jsEventEmitter;
}

// Reemits native state change events
function _emitNativeStateChangeEvent(params: any) {
  let newParams = { ...params };
  if (typeof params === 'string') {
    newParams = JSON.parse(params);
  }
  newParams.context = transformNativeStateMachineContext(newParams.context);
  _getJsEventEmitter().emit('Expo.updatesStateChangeEvent', newParams);
}

/**
 * Add listener for state change events
 * @hidden
 */
export const addUpdatesStateChangeListener = (
  listener: (event: UpdatesNativeStateChangeEvent) => void
) => {
  return _getJsEventEmitter().addListener('Expo.updatesStateChangeEvent', listener);
};

/**
 * Allows JS to emit a simulated native state change event (used in unit testing)
 * @hidden
 */
export const emitTestStateChangeEvent = (event: UpdatesNativeStateChangeEvent) => {
  _emitNativeStateChangeEvent(event);
};