Leon Chaewon Kong's dev blog

How to Set up Node/Express server with TypeScript


You must install TypeScript globally.

$ npm install -g typescript

If you got an permission error, try sudo prefix.

Project Initialization

Now, let’s create an npm project.

$ mkdir ts-node-server
$ cd ts-node-server
$ npm init -y

This will create package.json and other setting files.

Then run,

$tsc --init

to create TypeScript environment. tsconfig.json file will be initialized then, and you can configure settings for TypeScript.


Now is the time to create express app.

First, we need to install @types/express.

$ npm i @types/express

Create index.ts file to store code for your server, and type the code below.

import express from "express";

declare global {
  namespace NodeJS {
    interface ProcessEnv {
      NODE_ENV: string;
      PORT?: string;

class App {
  public application: express.Application;
  constructor() {
    this.application = express();

const app = new App().application;
const PORT = process.env.PORT || 4000;

// show "Successfully started" on browser when you visit localhost:4000
app.get("/", (req: express.Request, res: express.Response) => {
  res.send("Successfully started");

// show "Server is Running at >>> localhost:4000" on your terminal.
app.listen(PORT, () =>
  console.log(`Server is Running at >>> localhost:${PORT}`)

you may import express like import * as express from "express", if you got an error from module imports.

We use process.env.PORT as a port if it exists, else use 4000. In order to use this method, we need to declare namespace and interface globally by using declare global code block.

Then we created App class to generate express app.


In order to watch updates in your code while running the server, we need to use nodemon.

$ npm i -D nodemon ts-node

The -D flag implies the followed modules would be added to devDependencies.

Almost done. Add start script to package.json.

Your package.json would like:

  "name": "server",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "start": "nodemon index.ts"
  "author": "",
  "license": "ISC",
  "devDependencies": {
    "nodemon": "^2.0.2",
    "ts-node": "^8.6.2"
  "dependencies": {
    "@types/express": "^4.17.2"

Finally, it’s time to run your server.

Type npm run start, and go to “http://localhost:4000”.

You will see “Successfully started”, then you made it!