Let's setup an Express app using Typescript.

1. Install TSC, TSLint, and type declarations for NodeJS

• npm install --save-dev typescript tslint @types/node @tsconfig/node16
• Let's install express as well
  • npm install --save express

2. Write tsconfig.json

{
  "extends": "@tsconfig/node16/tsconfig.json",
  "compilerOptions": {
    "outDir": "dist"
  },
  "include": ["index.ts"]
}

3. Add npm run commands

We want to be able to run npm run build to compile typescript file into a javascript file.

Add "build": "./node_modules/.bin/tsc" under "scripts" key.

We also want to run npm run start to run the express app.

Add "start": "node ./dist" under "scripts" key.

The package.json file should look like this.

{
  "name": "typescript-nodejs",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "build": "./node_modules/.bin/tsc",
    "start": "node ./dist"
  },
  "author": "",
  "license": "ISC",
  "devDependencies": {
    "@tsconfig/node16": "^1.0.3",
    "@types/node": "^17.0.42",
    "tslint": "^6.1.3",
    "typescript": "^4.7.3"
  },
  "dependencies": {
    "express": "^4.18.1"
  }
}

4. Add index.ts with express.js

Add the following. THe code is from the express website.

const express = require('express');
const app = express();
const port = 3000;

app.get('/', (req, res) => {
  res.send('Hello World!');
});

app.listen(port, () => {
  console.log(`Example app listening on port ${port}`);
});

5. Compile and run

• Compile: npm run build
• Start: npm run start

You should see Example app listening on port 3000 printed in the console.

You can see the hello world when you go to localhost:3000.

You can find the code here.