setting-up-expressjs
Setting up and Using TypeScript with Express.js:
Let's break down each of these steps with corresponding TypeScript code examples where applicable:
Initial setup:
Install the necessary packages including TypeScript, Node.js, Express, and their type definitions.
- Example commands:
npm install typescript @types/node express @types/express
- Example commands:
tsconfig.json:
Create a
tsconfig.json
file tailored for Node.js.- Example
tsconfig.json
content:{
"compilerOptions": {
"module": "commonjs",
"esModuleInterop": true,
"target": "es2018",
"moduleResolution": "node",
"outDir": "./dist",
"strict": true
},
"include": ["src/**/*"],
"exclude": ["node_modules"]
}
- Example
TypeScript Node:
Use
ts-node
in development to execute TypeScript files.- Example command:
npx ts-node src/index.ts
- Example command:
Middleware types:
Type your middleware using types from
@types/express
.Example middleware:
import { Request, Response, NextFunction } from 'express';
const myMiddleware = (req: Request, res: Response, next: NextFunction) => {
// Middleware logic
next();
};
Route handlers:
Ensure your route handlers are properly typed.
- Example route handler:
app.get('/user/:id', (req: Request, res: Response) => {
const userId = req.params.id;
// Fetch user logic
res.json(user);
});
- Example route handler:
Error handling:
Create custom error handlers following the
ErrorRequestHandler
type.Example error handler:
import { ErrorRequestHandler } from 'express';
const errorHandler: ErrorRequestHandler = (err, req, res, next) => {
// Error handling logic
res.status(500).send('An error occurred');
};
Interface extension:
Extend the Express
Request
andResponse
interfaces when needed.Example interface extension:
import { Request, Response } from 'express';
interface RequestWithUser extends Request {
user?: User; // Custom property added to the request type
}
const getUserMiddleware = (req: RequestWithUser, res: Response, next: NextFunction) => {
// Middleware logic to add user to request
req.user = { id: 1, name: 'John Doe' };
next();
};
These steps and examples guide you through setting up a Node.js server using Express with TypeScript, ensuring type safety and taking advantage of TypeScript's features for a better development experience.
For each of these points, I'll explain how they can be applied in a TypeScript project, particularly for a Node.js and Express server:
Organizing routes:
Break down your server's routes into separate modules.
Example:
// In userRoutes.ts
import { Router } from 'express';
const router = Router();
router.get('/users', /* ... */);
router.post('/users', /* ... */);
export default router;
// In your main server file, e.g., app.ts
import userRoutes from './userRoutes';
app.use('/api', userRoutes);
Async functions:
Wrap async route handlers to handle rejections.
Example wrapper:
const asyncHandler = (fn) => (req, res, next) =>
Promise.resolve(fn(req, res, next)).catch(next);
// In your route
app.get('/users', asyncHandler(async (req, res) => {
// your async logic here
}));
Request validation:
Use runtime validation libraries alongside TypeScript types.
Example with
joi
:import Joi from 'joi';
const userSchema = Joi.object({
username: Joi.string().alphanum().min(3).max(30).required(),
// other validations
});
app.post('/users', (req, res, next) => {
const { error } = userSchema.validate(req.body);
if (error) return res.status(400).send(error.details);
// proceed with validated data
});
Environmental typing:
Type your environment variables for better safety.
Example:
interface Env {
NODE_ENV: 'development' | 'production';
PORT: string;
// other env variables
}
const env: Env = process.env as any;
Database interaction:
Utilize ORMs that have TypeScript support.
Example with TypeORM:
import { Entity, PrimaryGeneratedColumn, Column } from 'typeorm';
@Entity()
class User {
@PrimaryGeneratedColumn()
id: number;
@Column()
name: string;
// other columns
}
Project structure:
Maintain a clear and organized project structure.
- Suggested folder structure:
src/
controllers/
entities/
middlewares/
routes/
services/
utils/
app.ts
server.ts
- Suggested folder structure:
Testing:
Write tests using TypeScript.
- Example with Jest:
// In user.test.ts
describe('User routes', () => {
it('should create a new user', async () => {
// your test logic here, with types
});
});
- Example with Jest:
Building for production:
Set up scripts to compile and run your TypeScript app.
- Example
package.json
scripts:Make sure to test the JavaScript output in a production-like environment to catch any issues before deployment.{
"scripts": {
"build": "tsc",
"start": "node dist/app.js",
"dev": "ts-node src/app.ts"
}
}
- Example
By following these practices, you can leverage TypeScript's capabilities to create a more maintainable, type-safe backend environment using Node.js and Express.