Express.js: Building RESTful APIs

Setting Up Express

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const express = require('express');
const app = express();

app.use(express.json());

app.listen(3000, () => {
  console.log('Server running on port 3000');
});

Basic Routes

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// GET
app.get('/api/users', (req, res) => {
  res.json({ users: [] });
});

// POST
app.post('/api/users', (req, res) => {
  const user = req.body;
  res.status(201).json(user);
});

// PUT
app.put('/api/users/:id', (req, res) => {
  res.json({ id: req.params.id, ...req.body });
});

// DELETE
app.delete('/api/users/:id', (req, res) => {
  res.json({ deleted: req.params.id });
});

Middleware

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// Custom middleware
const authMiddleware = (req, res, next) => {
  const token = req.headers.authorization;
  if (token) {
    req.user = { id: 1 }; // Mock verification
    next();
  } else {
    res.status(401).json({ error: 'Unauthorized' });
  }
};

app.use(authMiddleware);

Error Handling

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app.use((err, req, res, next) => {
  console.error(err.stack);
  res.status(500).json({ error: 'Internal Server Error' });
});

Conclusion

Express makes building APIs simple and straightforward. Start with basics and grow from there.

Practical Implementation Guide

To apply express.js: building restful apis in production code, use this workflow:

1. Start with a minimal, testable implementation.
2. Validate edge cases and failure paths before optimization.
3. Add observability (logs, metrics, traces) so behavior is measurable.
4. Refactor for readability and maintainability after correctness is confirmed.

Common Mistakes and How to Avoid Them

• Over-optimizing too early instead of validating correctness first.
• Skipping boundary conditions and invalid input handling.
• Ignoring maintainability when introducing advanced patterns.
• Missing tests for regressions after refactoring.

Interview and Real-World Discussion Points

When discussing this topic in interviews or code reviews, explain:

• Why you selected a specific approach over alternatives.
• Complexity trade-offs in terms of performance and maintainability.
• How your implementation behaves under scale or failure.
• What tests and monitoring validate your solution.

SEO Keywords

nodejs, express, api, backend, coding tutorial, programming guide, developer best practices, software engineering

Final Checklist

• Core concept understood and applied correctly.
• Edge cases handled explicitly.
• Code is readable and documented where needed.
• Tests cover happy path and failure path behavior.