Overview

Today's focus: improved backend structure using proper error handling, created a global error middleware, and added validation for request bodies using Joi. Cleaned up the authentication middleware as well.

What I Learned Today

• How to create a global error-handling middleware
• Using try/catch with next(error) to propagate errors
• Validating input data with Joi schemas
• Sending clean and consistent error responses
• Improving readability and safety of routes
• Separating validation and auth logic into reusable middlewares

Key Concepts

• Error middleware has 4 parameters: (err, req, res, next)
• Validation should happen before database actions
• Joi helps enforce clean and predictable data structures
• Middleware ordering matters: validation → auth → route handler

Code Examples

Joi Validation Schema (Signup)

const Joi = require("joi");

const signupSchema = Joi.object({
  username: Joi.string().min(3).max(30).required(),
  email: Joi.string().email().required(),
  password: Joi.string().min(6).required()
});

Validation Middleware

const validateSignup = (req, res, next) => {
  const { error } = signupSchema.validate(req.body);
  if (error) return res.status(400).send(error.details[0].message);
  next();
};

Improved Auth Middleware