@uppy/companion/lib/server/emitter/index.js

OAuth helper and remote fetcher for Uppy's (https://uppy.io) extensible file upload widget with support for drag&drop, resumable uploads, previews, restrictions, file processing/encoding, remote providers like Dropbox and Google Drive, S3 and more :dog:

"use strict";
const nodeEmitter = require('./default-emitter');
const redisEmitter = require('./redis-emitter');
let emitter;
/**
 * Singleton event emitter that is shared between modules throughout the lifetime of the server.
 * Used to transmit events (such as progress, upload completion) from controllers,
 * such as the Google Drive 'get' controller, along to the client.
 */
module.exports = (redisClient, redisPubSubScope) => {
    if (!emitter) {
        emitter = redisClient
            ? redisEmitter(redisClient, redisPubSubScope)
            : nodeEmitter();
    }
    return emitter;
};