TypeScript Setup

TypeScript

• Install typescript globally

npm i -g typescript

cd express-ts
# initialize a tsconfig.json file
tsc --init

• Change the following values

tsconfig.json

"outDir": "./build" /* Redirect output structure to the directory. */
"moduleResolution": "node", /* Specify module resolution strategy: 'node' (Node.js) or 'classic' (TypeScript pre-1.6). */

• Change target to es6 for modern projects

tsconfig.json

"target": "es6", /* Specify ECMAScript target version: 'ES3' (default), 'ES5', 'ES2015', 'ES2016', 'ES2017', 'ES2018', 'ES2019', 'ES2020', or 'ESNEXT'. */

---

.gitignore

.gitignore

# build files
build

# node modules
node_modules

#editor
.vscode

#config
.env

---

npm

• Initialize a npm project

npm init -y

• Install dependencies

npm i express typescript @types/node @types/express

• Install dev dependencies

npm i -D ts-node nodemon

• Edit scripts in package.json

package.json

"scripts": {
    "start": "tsc && node ./build/app.js",
    "dev": "nodemon app.ts",
    "build": "tsc -p ."
},

• Use npm run dev for development
• Use npm run start for production

---

Express app

• Create app.ts in root directory
• ES6 import can be used

app.ts

// lib/app.ts
import express from 'express';

// Create a new express application instance
const app: express.Application = express();

app.get('/', function (req: express.Request, res: express.Response, next: express.NextFunction) {
  res.send('Hello TypeScript!');
});

const PORT = process.env.PORT || 3000

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

• Or import named exports as below

app.ts

import express, { Application, Request, Response, NextFunction } from 'express';

const app: Application = express();

app.get('/', function (req: Request, res: Response, next: NextFunction) {
  res.send('Hello TypeScript!');
});