Including JavaScript class definition from another file in Node.js
Javascriptnode.jsJavascript Problem Overview
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?
Javascript Solutions
Solution 1 - Javascript
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()
Solution 2 - Javascript
Using ES6, you can have user.js
:
export default class User {
constructor() {
...
}
}
And then use it in server.js
const User = require('./user.js').default;
const user = new User();
Solution 3 - Javascript
Modify your class definition to read like this:
exports.User = function (socket) {
...
};
Then rename the file to user.js
. Assuming it's in the root directory of your main script, you can include it like this:
var user = require('./user');
var someUser = new user.User();
That's the quick and dirty version. Read about CommonJS Modules if you'd like to learn more.
Solution 4 - Javascript
Another way in addition to the ones provided here for ES6
module.exports = class TEST{
constructor(size) {
this.map = new MAp();
this.size = size;
}
get(key) {
return this.map.get(key);
}
length() {
return this.map.size;
}
}
and include the same as
var TEST= require('./TEST');
var test = new TEST(1);
Solution 5 - Javascript
If you append this to user.js
:
exports.User = User;
then in server.js
you can do:
var userFile = require('./user.js');
var User = userFile.User;
http://nodejs.org/docs/v0.4.10/api/globals.html#require
Another way is:
global.User = User;
then this would be enough in server.js
:
require('./user.js');