How to split code into multiple modules?

Question

I know that it is possible to separate functions into other files on Node, called modules, as follows:

js server.

var http = require("http");
var servidor = http.createServer();
var porta = 3000;

var corpo = require("./modulo-corpo.js");

servidor.on("request", function (request, response) {
    var resposta = corpo.getCorpo();
    response.writeHead(200, {
        "Content-Type": "text/plain",
        "Content-Length": resposta.length
    });
    response.end(resposta);
});

servidor.listen(porta, function () {
    console.log("servidor da bete, rodando na porta " + porta);
});

modulo-corpo.js

var n = 0;
exports.getCorpo = function() {
    return "bete beijou " + ++n + " bebados barrigudos bebendo bebidas baratas";
}

I would like to know what resources are available for code organization on the Node.

A practical example of what I imagine would be to access the variable n body module, as if it had been declared in the file servidor.js.

The intention is to organize the code, making, for example, a module only with variables, another only with routes, etc., so that it is easier to be treated/changed/expanded in the future.

Answer 1

The way the n is inaccessible to other modules and n behaves as private variable module. This is very useful in many cases.

If you want to consult the n you have to make a getter that could be so:

var n = 0;
exports.getCorpo = function() {
  return "bete beijou " + (++n) + " bêbados barrigudos bebendo bebidas baratas";
}
Object.defineProperty(exports, 'n', {
  get: function() {
    return n;
  }
});

So the module gets a property n that will fetch the real value of n cannot be overwritten.

If you want to manipulate n you can do a Setter too:

Object.defineProperty(exports, 'n', {
  get: function() {
    return n;
  },
  set: function(valor) {
    n = valor;
  }
});

---

I made an online example that you can download and test (link). The idea is:

file: server.js

const http = require('http');
const express = require('express');
const app = express();
const variaveis = require("./variaveis");
const rotas = require("./rotas")(app);

const server = app.listen(process.env.PORT || 3000, function(){
    const host = server.address().address;
    const port = server.address().port;
    console.log('App listening at http://%s:%s', host, port);
});

file: variables.js

let contador = 0;

const variaveis = Object.create(Object.prototype, {
  carregamento: { // data em que o servidor começou a correr
    writable: false,
    configurable: false,
    value: new Date() 
  },
  contador: {
    configurable: false,
    get: function() { return contador++ },
    set: function(valor) {
      contador = valor;
    }
  }
});

module.exports = variaveis;

file: routes.js

const variaveis = require("./variaveis");
module.exports = (app) => {
    app.use('/', (req, res) => {
       res.end('O contador esta em: ' + variaveis.contador); 
    });

    app.use(function(req, res, next){
        console.log(req.originalUrl);
    });
}

With this structure it is possible for any file to know the value of contador as well as changing its value outside the file where that variable is inserted.