Express

express-async-errors

When to Use

• Microservices: Lightweight and fast.
• REST APIs: The standard for building JSON APIs in Node.
• Learning: The best way to learn how HTTP works in Node.

Quick Start (Express 5)

import express from "express";
const app = express();

// Express 5 handles async errors automatically!
app.get("/", async (req, res) => {
  const user = await db.getUser(); // If this throws, Express catches it.
  res.json(user);
});

app.listen(3000);

Core Concepts

Middleware

req

res

next

Log -> Auth -> BodyParse -> RouteHandler

Routing

app.get()

app.post()

Best Practices (2025)

• Upgrade to Express 5: Native Promise support is a game changer for cleaner code.
• Use

  helmet

  : Security headers are mandatory.
• Structure properly: Don't put everything in

  app.js

  . Use

  express.Router()

  .

• Don't stick to CommonJS: Express 5 supports ESM. Use

  import

  .
• Don't use

  body-parser

  separate package: Use

  express.json()

  (included since v4, standard in v5).

References

• Express 5 Migration Guide