How to dynamically select module with modern nodeJS?

Question

I am using node --experimental-modules test.mjs (NodeJs v11.9.0).

There are many options to implement the same class, and I need to swith by terminal,

Answer 1

Modern Javascript (ES6+) implementations are under construction, some syntax are working with NodeJS (node --experimental-modules) and good browsers, other not.

This is the only way to do without cost of "load all" (see @Markus solution), but with the cost of non-global import, needs an ugly block to define scope and assyncronous operation... First step is to understand the basic impor block syntax:

import('./MyClass-v3.mjs').then(({default: MyClass}) => {
    // can use MyClass only here in this block
    let x = new MyClass();
    console.log("DEBUG=",x);
});

Them, putting all together, the argv selection and the optional imports.

Solution

const classes = {
  a: './MyClass-v1.mjs'
  ,b: './MyClass-v3.mjs'
  ,c: './MyClass-v3.mjs'
};
import(classes[process.argv[2]] || classes.c ).then(({default: MyClass}) => {
    let x = new MyClass();
    console.log("DEBUG=",x);
});

PS: some of the magic (no rational) is to use ({default: MyClass}) instead (MyClass).

---

Thanks

To @Bergi (!), for explain this solution (see question comments).

Answer 2

import ClassV1 from './MyClass-v1.mjs';
import ClassV2 from './MyClass-v2.mjs'; 
import ClassV3 from './MyClass-v3.mjs';

const classes = {
  a: ClassV1,
  b: ClassV2
}

const Class = classes[process.argv[2]] || ClassV2;

You could also write an index file with all the classes and do an import * as classes from 'classes.mjs';.