How to properly export an ES6 class in Node 4?

Question

I defined a class in a module:

"use strict";

var AspectTypeModule = function() {};
module.exports = AspectTypeModule;

var AspectType = class AspectType {
    // ...    
};

module.export.AspectType = AspectType;

But I get the following error message:

TypeError: Cannot set property 'AspectType' of undefined
    at Object.<anonymous> (...\AspectType.js:30:26)
    at Module._compile (module.js:434:26)
    ....

How should I export this class and use it in another module? I have seen other SO questions, but I get other error messages when I try to implement their solutions.

Answer 1

If you are using ES6 in Node 4, you cannot use ES6 module syntax without a transpiler, but CommonJS modules (Node's standard modules) work the same.

module.export.AspectType

should be

module.exports.AspectType

hence the error message "Cannot set property 'AspectType' of undefined" because module.export === undefined .

Also, for

var AspectType = class AspectType {
    // ...    
};

can you just write

class AspectType {
    // ...    
}

and get essentially the same behavior.

Answer 2

// person.js
'use strict';

module.exports = class Person {
   constructor(firstName, lastName) {
       this.firstName = firstName;
       this.lastName = lastName;
   }

   display() {
       console.log(this.firstName + " " + this.lastName);
   }
}

// index.js
'use strict';

var Person = require('./person.js');

var someone = new Person("First name", "Last name");
someone.display();

Answer 3

With ECMAScript 2015 you can export and import multiple classes like this

class Person
{
    constructor()
    {
        this.type = "Person";
    }
}

class Animal{
    constructor()
    {
        this.type = "Animal";
    }
}

module.exports = {
    Person,
    Animal
};

then where you use them:

const { Animal, Person } = require("classes");

const animal = new Animal();
const person = new Person();

In case of name collisions, or you prefer other names you can rename them like this:

const { Animal : OtherAnimal, Person : OtherPerson} = require("./classes");

const animal = new OtherAnimal();
const person = new OtherPerson();

Answer 4

Use

// aspect-type.js
class AspectType {

}

export default AspectType;

Then to import it

// some-other-file.js
import AspectType from './aspect-type';

Read http://babeljs.io/docs/learn-es2015/#modules for more details

Answer 5

class expression can be used for simplicity.

 // Foo.js
'use strict';

// export default class Foo {}
module.exports = class Foo {}

-

// main.js
'use strict';

const Foo = require('./Foo.js');

let Bar = new class extends Foo {
  constructor() {
    super();
    this.name = 'bar';
  }
}

console.log(Bar.name);

Answer 6

I simply write it this way

in the AspectType file:

class AspectType {
  //blah blah
}
module.exports = AspectType;

and import it like this:

const AspectType = require('./AspectType');
var aspectType = new AspectType;

Answer 7

Several of the other answers come close, but honestly, I think you're better off going with the cleanest, simplest syntax. The OP requested a means of exporting a class in ES6 / ES2015. I don't think you can get much cleaner than this:

'use strict';

export default class ClassName {
  constructor () {
  }
}

Answer 8

I had the same problem. What i found was i called my recieving object the same name as the class name. example:

const AspectType = new AspectType();

this screwed things up that way... hope this helps

Answer 9

Sometimes I need to declare multiple classes in one file, or I want to export base classes and keep their names exported because of my JetBrains editor understands that better. I just use

global.MyClass = class MyClass { ... };

And somewhere else:

require('baseclasses.js');
class MySubclass extends MyClass() { ... }