How to create a simple (Hello World) node.js TypeScript project with ES6 modules?

Issue

Imagine a very simple program with a main file and some functions in a separate file, using ES6 modules and intended to be run with node.js.

my-utils.ts:

import * as fs from "fs";

export function readSimpleFile() {
    return fs.fileReadSync("hello.txt", "utf-8");
}

main.ts:

import {readSimpleFile} from "./my-utils"

console.log(readSimpleFile());

What is the minimum set of files I need to add to the project and commands I have to run to get it building, running and checking types?

Solution

If you are to run a typescript project with node you need to have at least node, npm and typescript installed on your plateform.

Using an IDE to setup the project

Using intelliJ IDEA or Webstorm (they are the ones I know the best), the compilation of typescript into javascript is done automatically; you only need to do some settings.

Let us assume you have a file called project.ts containing your hello world code; IDEA or Webstorm will compile your code to project.js. Then you will only need to do node project.js to run your project.

Doing everything from scratch

First you need to know where exactly your npm packages are installed globally. This command can help you identify the path: npm config get prefix. In this folder, you should have a nodes_modules subfolder that contains the typescript module. If there is no typescript module, that is because you did not install typescript globally (npm install -g typescript).

Then you have to add the path of the bin of typescript subfolder in your environment variable.

Now you can compile the project with typescipt: tsc project.ts and you can run it node project.js.

Since you are using node function like fs you will need to install node typings npm install @types/node --save-dev before compiling with tsc.

Compilation option

To enable or disable all strict type checking options, you might need to use compilation option. You have to create the file in which you will specify the compilation option: tsc --init will create a tsconfig.json in which you can specify what behaviour you would like to have during the compilation of your app. All options are listed here.

Answered By - edkeveked