Add Input Validation Middleware in Express using Zod

Use this AI prompt to create Zod-based validation middleware for Express APIs to ensure type safety and clean error responses.

🧠 What This Prompt Does

This prompt helps you add robust input validation middleware to your Express routes using Zod.
It improves backend safety, prevents bad requests, and keeps your controllers clean.

💬 The Prompt

You are a Node.js developer.
Generate a Zod validation middleware for Express that:

- Validates request body against schema
- Returns 400 for invalid data
- Attaches validated data to req.body
- Works for any route

🚀 Example Output (AI Generated)

import { z } from 'zod';

export const validateBody = (schema) => (req, res, next) => {
  try {
    req.body = schema.parse(req.body);
    next();
  } catch (error) {
    if (error instanceof z.ZodError) {
      return res.status(400).json({ errors: error.errors });
    }
    next(error);
  }
};

// Example usage:
const userSchema = z.object({
  name: z.string().min(2),
  email: z.string().email(),
});

app.post('/users', validateBody(userSchema), (req, res) => {
  res.status(201).json({ user: req.body });
});

📘 When to Use This Prompt

• When adding request body validation to Express routes.
• To prevent invalid payloads reaching business logic.
• When standardizing API input schemas across endpoints.

💡 Best Practices

• Define schemas per entity for clarity.
• Centralize validators for reuse across routes.
• Always validate query and params when necessary.
• Combine this with centralized error handling.

🏁 Summary

This prompt generates a Zod-powered validation layer for Express apps, ensuring your APIs handle data safely and predictably.