JSON ⇄ Zod & Valibot Converter

Static Typing vs Runtime Validation

In TypeScript, interface definitions like interface User { email: string } are completely erased when compiled to JavaScript. If an API endpoint receives invalid data, a standard interface cannot throw an error or guard against runtime crashes.

Schema libraries like Zod and Valibot validate data at runtime, parsing raw objects and safely narrowing types:

Code Recipes

Zod Validation in Node.js / Express

import { z } from 'zod';

const UserSchema = z.object({
  id: z.string().uuid(),
  email: z.string().email(),
  role: z.enum(['admin', 'member'])
});

// Safe parsing without try/catch
const result = UserSchema.safeParse(req.body);
if (!result.success) {
  return res.status(400).json(result.error.flatten());
}
const user = result.data; // Fully typed as { id, email, role }

Valibot Tree-Shakeable Validation

import * as v from 'valibot';

const UserSchema = v.object({
  id: v.pipe(v.string(), v.uuid()),
  email: v.pipe(v.string(), v.email())
});

const user = v.parse(UserSchema, input);