A simple way to broardcast message in react app, use for low level layer to communicate with higher level (app/ui layer)

eventEmitter.ts

/**
 * A simplify version of https://github.com/primus/eventemitter3
 */
const listenersMap: { [id: string]: Array<(...params: any[]) => void> } = {};

function addListener(eventName: string, listener: (...params: any[]) => void) {
  listenersMap[eventName] = listenersMap[eventName] || [];
  listenersMap[eventName].push(listener);
}

function removeListener(eventName: string, listener: (...params: any[]) => void) {
  let lis = listenersMap[eventName];
  if (!lis) return;

  for (let i = lis.length - 1; i >= 0; i--) {
    if (lis[i] === listener) {
      lis.splice(i, 1);
      break;
    }
  }
}

function removeAllListeners(eventName: string) {
  listenersMap[eventName] = [];
}

function notify<T = any>(eventName: string, ...params: T[]) {
  let listeners = listenersMap[eventName];
  if (!listeners) return false;
  listeners.forEach(fnc => {
    fnc(...params);
  });
  return true;
}

const EventEmitter = {
  addListener,
  removeListener,
  removeAllListeners,
  notify,
};

export default EventEmitter;