typia

Typia

// RUNTIME VALIDATORS
export function is<T>(input: unknown): input is T; // returns boolean
export function assert<T>(input: unknown): T; // throws TypeGuardError
export function assertGuard<T>(input: unknown): asserts input is T;
export function validate<T>(input: unknown): IValidation<T>; // detailed

// JSON FUNCTIONS
export namespace json {
  export function schema<T>(): IJsonSchemaUnit<T>; // JSON schema
  export function assertParse<T>(input: string): T; // type safe parser
  export function assertStringify<T>(input: T): string; // safe and faster
}

// AI FUNCTION CALLING HARNESS
export namespace llm {
  // collection of function calling schemas + validators/parsers
  export function application<Class>(): ILlmApplication<Class>;
  export function structuredOutput<P>(): ILlmStructuredOutput;
  // typed questions for evaluation models + checked answer decoder
  export function evaluation<T>(): ILlmEvaluation<T>;
  // lenient json parser + type coercion
  export function parse<T>(str: string): T;
}

// PROTOCOL BUFFER
export namespace protobuf {
  export function message<T>(): string; // Protocol Buffer message
  export function assertDecode<T>(buffer: Uint8Array): T; // safe decoder
  export function assertEncode<T>(input: T): Uint8Array; // safe encoder
}

// RANDOM GENERATOR
export function random<T>(g?: Partial<IRandomGenerator>): T;

typia is a transformer library supporting below features:

• Super-fast Runtime Validators
• Enhanced JSON schema and serde functions
• LLM function calling harness
• Protocol Buffer encoder and decoder
• Random data generator

Write the type on the left, and typia compiles it into the validator on the right — at build time, with no schema and no runtime reflection.

Setup

Install typia with the ttsc toolchain.

# install
npm i typia
npm i -D ttsc typescript

# build
npx ttsc

# run a script directly
npx ttsx src/index.ts

You must use ttsc and ttsx. The stock tsc, ts-node, and tsx cannot apply the typia transform, so they will not work.

For bundler integration (Vite, Next.js, Webpack, Rollup, esbuild, …), use @ttsc/unplugin.

Transformation

If you call typia function, it would be compiled like below.

This is the key concept of typia, transforming TypeScript type to a runtime function. The typia.is<T>() function is transformed to a dedicated type checker by analyzing the target type T in the compilation level.

This feature enables developers to ensure type safety in their applications, leveraging TypeScript’s static typing while also providing runtime validation. Instead of defining additional schemas, you can simply utilize the pure TypeScript type itself.

//----
// examples/checkString.ts
//----
import typia, { tags } from "typia";
export const checkString = typia.createIs<string>();

//----
// examples/checkString.js
//----
import typia from "typia";
export const checkString = (() => {
  return (input) => "string" === typeof input;
})();

Sponsors

Thanks for your support.

Your donation encourages typia development.

Playground

You can experience how typia works by playground website:

• 💻 https://typia.io/playground

Guide Documents

Check out the document in the website:

🏠 Home

• Introduction
• Setup
• Pure TypeScript

📖 Features

• Runtime Validators
  • assert() function
  • is() function
  • validate() function
  • Functional Module
  • Special Tags
• Enhanced JSON
  • JSON Schema
  • stringify() functions
  • parse() functions
• LLM Function Calling Harness
  • application() function
  • structuredOutput() function
  • evaluation() function
  • HttpLlm module
  • LlmJson module
• Protocol Buffer
  • Message Schema
  • decode() functions
  • encode() functions
• Random Generator
• Miscellaneous

🔗 Appendix

• API Documents
• Utilization Cases
  • MCP
  • Vercel AI SDK
  • LangChain
  • NestJS
  • tRPC
• ⇲ Benchmark Result
• ⇲ dev.to Articles

Inspired By

• typescript-is