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Alex Spinov
Alex Spinov

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TypeBox Has a Free API — JSON Schema Validation at TypeScript Speed

#webdev #javascript #tutorial #typescript

TypeBox creates JSON Schema types that are also TypeScript types. One definition, two systems — compile-time safety and runtime validation from the same code.

What is TypeBox?

TypeBox generates standard JSON Schema objects that double as TypeScript types. It works with any JSON Schema validator (Ajv, etc.) while giving you full TypeScript inference.

Quick Start 

npm install @sinclair/typebox
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import { Type, Static } from '@sinclair/typebox';
import { Value } from '@sinclair/typebox/value';

const User = Type.Object({
  name: Type.String(),
  email: Type.String({ format: 'email' }),
  age: Type.Number({ minimum: 0 }),
});

type User = Static<typeof User>;
// { name: string; email: string; age: number }

// Validate
const isValid = Value.Check(User, { name: 'Alice', email: 'a@b.com', age: 30 });
// true

// Get errors
const errors = [...Value.Errors(User, { name: 123 })];
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Common Types 

// Primitives
Type.String();
Type.Number();
Type.Boolean();
Type.Null();

// Arrays and Tuples
Type.Array(Type.String());
Type.Tuple([Type.String(), Type.Number()]);

// Unions and Intersections
Type.Union([Type.String(), Type.Number()]);
Type.Intersect([UserBase, UserProfile]);

// Optional and Readonly
Type.Object({
  required: Type.String(),
  optional: Type.Optional(Type.String()),
  readonly: Type.Readonly(Type.String()),
});

// Enums
Type.Union([
  Type.Literal('active'),
  Type.Literal('inactive'),
]);
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Using with Ajv (Maximum Performance) 

import Ajv from 'ajv';
import { Type } from '@sinclair/typebox';

const ajv = new Ajv();
const schema = Type.Object({
  id: Type.String({ format: 'uuid' }),
  items: Type.Array(Type.Object({
    name: Type.String(),
    price: Type.Number({ minimum: 0 }),
  })),
});

const validate = ajv.compile(schema);

if (validate(data)) {
  // data is typed as Static<typeof schema>
}
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Value Utilities 

import { Value } from '@sinclair/typebox/value';

// Create default values
const defaultUser = Value.Create(User);
// { name: '', email: '', age: 0 }

// Cast (coerce) data
const casted = Value.Cast(User, { name: 123, extra: true });
// { name: '123', email: '', age: 0 }

// Clone
const cloned = Value.Clone(data);

// Diff and Patch
const diff = Value.Diff(oldUser, newUser);
const patched = Value.Patch(oldUser, diff);
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Why TypeBox?

  • Standards-based — generates real JSON Schema (use with any validator)
  • Zero dependencies — tiny bundle size
  • Fastest — compiled validators outperform Zod by 1000x+
  • Elysia/Fastify native — built-in TypeBox support

Need structured data from the web? Check out my Apify scrapers for ready-to-use data extraction tools, or email spinov001@gmail.com for custom solutions.

TypeBox or Zod — which do you prefer? Let me know in the comments!

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