Common mistakes to avoid while working with Express.js

Here are code snippets illustrating some common mistakes in Express.js along with their solutions:

1. Improper Error Handling:

Mistake:

app.get('/users', (req, res) => {
  // Logic to fetch users
  // If an error occurs:
  res.status(500).send('Internal Server Error');
});

Solution:

app.get('/users', (req, res, next) => {
  // Logic to fetch users
  // If an error occurs:
  next(new Error('Unable to fetch users'));
});

// Error handling middleware
app.use((err, req, res, next) => {
  res.status(500).send({ error: err.message });
});

2. Neglecting Security Measures:

Mistake:

// Handling a POST request without data validation
app.post('/login', (req, res) => {
  const username = req.body.username;
  const password = req.body.password;
  // Perform login without validating input
});

Solution:

const { body, validationResult } = require('express-validator');

// Data validation middleware
app.post('/login', [
  body('username').isLength({ min: 5 }),
  body('password').isLength({ min: 8 }),
], (req, res) => {
  const errors = validationResult(req);
  if (!errors.isEmpty()) {
    return res.status(400).json({ errors: errors.array() });
  }
  // Perform login after validating input
});

3. Using Synchronous Operations:

Mistake:

app.get('/data', (req, res) => {
  const result = fetchData(); // Synchronous operation
  res.json(result);
});

Solution:

app.get('/data', async (req, res) => {
  try {
    const result = await fetchData(); // Asynchronous operation
    res.json(result);
  } catch (error) {
    res.status(500).send('Error fetching data');
  }
});

These examples demonstrate how to handle errors, implement data validation, and use asynchronous operations properly within Express.js to avoid common mistakes and ensure better code quality and security.