Zod Has a Free API: TypeScript-First Schema Validation That Actually Works

#typescript #validation #api #javascript

Why Zod

Zod validates data AND gives you TypeScript types from schemas. Define once, validate at runtime, get types at compile time. No more duplicating types and validation logic.

Install

npm install zod

Basic Schemas

import { z } from 'zod';

const UserSchema = z.object({
  name: z.string().min(2),
  email: z.string().email(),
  age: z.number().int().min(18).max(120),
  role: z.enum(['admin', 'user', 'moderator']),
  bio: z.string().optional(),
});

type User = z.infer<typeof UserSchema>;
// { name: string; email: string; age: number; role: 'admin'|'user'|'moderator'; bio?: string }

const user = UserSchema.parse({
  name: 'Alice',
  email: 'alice@example.com',
  age: 30,
  role: 'admin',
});

API Validation

import express from 'express';
import { z } from 'zod';

const CreateOrderSchema = z.object({
  productId: z.string().uuid(),
  quantity: z.number().int().positive(),
  coupon: z.string().optional(),
});

app.post('/orders', (req, res) => {
  const result = CreateOrderSchema.safeParse(req.body);
  if (!result.success) {
    return res.status(400).json({ errors: result.error.flatten() });
  }
  const order = result.data; // Fully typed!
  // ...
});

Transform and Refine

const DateSchema = z.string().transform((s) => new Date(s));

const PasswordSchema = z.string()
  .min(8)
  .refine((pw) => /[A-Z]/.test(pw), 'Must contain uppercase')
  .refine((pw) => /[0-9]/.test(pw), 'Must contain number');

const PaginationSchema = z.object({
  page: z.coerce.number().int().positive().default(1),
  limit: z.coerce.number().int().min(1).max(100).default(20),
});

Key Features

Type inference — z.infer gives TypeScript types from schemas
Runtime validation — parse() and safeParse()
Composable — .extend(), .merge(), .pick(), .omit()
Transforms — coerce, transform, preprocess
Error formatting — flatten(), format()
Zero dependencies — tiny bundle

Resources

Need to extract API schemas, validation patterns, or TypeScript type data? Check out my Apify tools or email spinov001@gmail.com for custom solutions.

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