Question

I’m writing a simple server for Node.js and I’m using my own class called User which looks like:

function User(socket) {
    this.socket = socket;
    this.nickname = null;

    /* ... just the typical source code like functions, variables and bugs ... */

    this.write = function(object) {
        this.socket.write(JSON.stringify(object));
    }
};

and then later in the process I’m instantiating it a lot:

var server = net.createServer(function (socket) {
    /* other bugs */
    var user = new User(socket);
    /* more bugs and bad practise */
});

Can I move my User class definition to another javascript file and “include” it somehow?

Answer 1

You can simply do this:

user.js

class User {
  //...
}

module.exports = User //  Export class

server.js

const User = require('./user.js')

let user = new User()

This is called CommonJS module.

ES Modules

Since Node.js version 14 it’s possible to use ES Modules with CommonJS. Read more about it in the ESM documentation.

user.mjs ( extension is important)

export default class User {}

server.mjs

import User from './user.mjs'

let user = new User()