20.09 From NodeTS to JS

What are the differences?

Well that depends on which version of Javascript you are changing into. You have 2 types that I am going to cover. There might be more that I don’t know anything about.

• ES modules
• CommonJS modules On default Node will use CommonJS. But you can decide to use ES modules (ECMAScript modules) instead if you prefer that.

This article doesn’t dive that deep. for an deeper explanation, and a way to even combine the 2, here is an article.

Common changes

• Well of coarse the file type changes, server.ts is typescript only.
• You need to remove typing from everything, this includes: private, public, readonly. And Interfaces are not a thing in JavaScript.
• To use private methods/fields you have to put an # in front of it:

#connections = [];

Note: Ctrl+F might not change all variables from variable to #variable in vscode.

ES modules

ES modules keeps the same structure to importing modules:

import * as mongodb from "mongodb";
 
import { compare } from 'bcrypt';

The same is to say for the exporting of modules:

export const sessionTokenJsonSchema = {}
 
export class UserHandler { ... }
 
export async function connectToDatabase(uri) {
    ...
}

But you have to change your file from server.ts to server.mjs. Or you must set "type":"module" in the package.json, then you can use server.js.

CommonJS

This uses the server.js instead of server.ts.

Imports change in CommonJS. Instead of using the Typescript/ES modules structure, you’ll have to do it the following way to export:

module.exports.add = function(a, b) {
        return a + b;
} 
 
module.exports.subtract = function(a, b) {
        return a - b;
}

and the following way to import:

const {add, subtract} = require('./util')
 
console.log(add(5, 5)) // 10
console.log(subtract(10, 5)) // 5