Steps to create a barebones Express app with TypeScript and ESLint.
A sample app setup is available here. To clone it locally, run:

npx degit metamodal/blog/quick-express-typescript-setup/example express-ts-project

Else follow along to setup the project manually.

Step 1

Create an npm project:

mkdir express-ts-project
cd express-ts-project
npm init -y

Step 2

Install dependencies:

# Express-related deps
npm install express cors

# Tooling
npm install -D typescript eslint nodemon ts-node @typescript-eslint/eslint-plugin @typescript-eslint/parser

# Typings
npm i -D @types/cors @types/express @types/node

• cors: to allow cross-origin requests
• ts-node: to run TypeScript programs directly from the terminal (instead of having to transpile to JavaScript first)
• nodemon: to run your project in "watch" mode, meaning the program is automatically restarted every time you change your code
• @typescript-eslint/parser: allows ESLint to understand TypeScript syntax
• @typescript-eslint/eslint-plugin: loads the ESLint rules defined by you

Step 3

Create a file named tsconfig.json in the root of your project and paste the following config:

{
  "compilerOptions": {
    "lib": ["es2018"],
    "module": "commonjs",
    "target": "es2018",

    "strict": true,
    "esModuleInterop": true,
    "skipLibCheck": true,
    "forceConsistentCasingInFileNames": true,
    "sourceMap": true,
    "outDir": "dist"
  },
  "include": ["src/**/*"],
  "exclude": ["node_modules", "**/*.spec.ts"]
}

Step 4

Create a file named .eslintrc in the root of your project, and paste the following config:

{
  "root": true,
  "parser": "@typescript-eslint/parser",
  "plugins": [
    "@typescript-eslint"
  ],
  "extends": [
    "eslint:recommended",
    "plugin:@typescript-eslint/recommended"
  ]
}

Step 5

Create a folder named src and inside it a file src/index.ts. Paste the following in index.ts:

import express from "express";
import cors from "cors";

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

app.use(cors({ origin: true }));

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

app.listen(port, () => console.log("Listening on port " + port));

Step 6

Add the following in the scripts object in package.json:

"scripts": {
  "build": "tsc",
  "start": "nodemon src/index.ts"
}

Step 7

From the root of your project, run the command:

npm start

Go to http://localhost:3000 on your browser. If you see "Hello World!" printed on your screen, everything has worked correctly.

Typos? Improvements?

Thanks for reading. If you notice any typos or would like to suggest improvements, please feel free to either create an issue or PR here.