Nodejs: How to keep an updated list accessible between files

Question

In a Nodejs application with Express/EJS, I need to keep an updated list and I would like that whenever the user accesses my root route, that is the INDEX page, he could see this updated list. To summarize I put together the script below, which is responsible for updating the client list (but it doesn’t have to be the way I put it together...):

Client list update script:

// clients_list.js ============================================================
const tls = require('tls');

var clients = [];// Essa será a minha lista de clientes <<<===========
var aa = [{name: "aaaaaaaa"}, {name: "bbbbbbbb"}];

const server = tls.createServer(options, (myObj) => {

   myObj.on('beginEvent', (anotherObj) => {
      // Adiciona um cliente a cada evento
      clients.push(anotherObj);
   })

   myObj.on('endEvent', (anotherObj) => {
      // Remove um cliente a cada evento
      clients.splice(clientes.indexOf(anotherObj), 1);      
   })

});

module.exports = { server, clients, aa };

EXPRESS "app.js" file, where I want the list to be accessible and always updated:

// app.js do EXPRESS ==========================================================

const app = express();
// vários outros requires...
const indexRouter = require('./routes/index');

// Importação do servidor "serverCLIENTS.server" e da lista "serverCLIENTS.clients"
const serverCLIENTS = require('./clients_list'); 

// um monte de coisas....


// Minha rota raiz
app.use('/', indexRouter); // <<<========= PRETENDO QUE ESTA ROTA EXIBA A LISTA "serverCLIENTS.clients"


// um monte de coisas....

module.exports = app;

QUESTION: How do I make this list "clients" remain visible and up to date in my application?

Will the way is to make one middleware of this my script clients_list.js?

Answer 1

If you want to share a property between several modules of your application, one way is to use the Singleton Pattern applied to Node, defining a module that contains the single instance, which will be consumed and changed by several other modules.

e. g. :

Defining a Singleton with an array:

// singleton.js
const names = ['Joana', 'Jorge'];

module.exports.names = names;

consuming it in module A:

// singletonconsumer.js
const names = require('./singleton').names;

function seeNames() {
    console.log(names);
}

module.exports.seeNames = seeNames;

Consuming and changing in module B:

// index.js 
const names = require('./singleton').names;
const seeNames = require('./singletonconsumer').seeNames;

print();

names.push('fernanda');

print();

function print() {
    console.log(names);
    seeNames();
}

The result of the print:

Example running: https://repl.it/@spartanroger/Node-Patterns

Link about Twitter with Node : Rising stack Nodejs and Design Patterns