typia for TypeScript: Complete Guide with Examples

What is typia and why is it needed?

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typia is a powerful library for TypeScript that provides runtime type validation with a unique feature: it generates validation code at compile-time, not at runtime. This makes it one of the fastest data validation libraries in the TypeScript ecosystem.

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Main problems that typia solves:

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• Performance: Unlike popular libraries (zod, yup, io-ts), typia does not use reflection or decorators. Instead, it generates optimized validation code at build time, providing a 10–100x speed increase.
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• Type Safety: You get a guarantee that data coming from external sources (API, databases, forms) matches your TypeScript interfaces.
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• Minimal Boilerplate: You don't need to write separate validation schemas — typia uses your existing TypeScript types.
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• Support for Complex Types: Union, intersection, conditional types, mapped types — all work "out of the box".
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The library is especially useful for:

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• Backend development on Node.js with TypeScript
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• Frontend applications where form validation or API response validation is required
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• Microservice architecture where serialization/deserialization speed is important
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• Projects where performance and type safety are critical
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Installation

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Installing typia consists of two steps: the library itself and the TypeScript transformer (compiler).

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Step 1. Installation via npm

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npm install typia\n# or\nyarn add typia\n# or\npnpm add typia

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Step 2. Installing the transformer

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npm install --save-dev typia-transform\n# or\nyarn add -D typia-transform\n# or\npnpm add -D typia-transform

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Step 3. Configuring tsconfig.json

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Add the plugin to your tsconfig.json:

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{\n  "compilerOptions": {\n    "plugins": [\n      {\n        "transform": "typia-transform"\n      }\n    ]\n  }\n}

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Step 4. Using with ttypescript (recommended)

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Install ttypescript for automatic transformation:

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npm install --save-dev ttypescript

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Then replace tsc with ttsc in your package.json scripts:

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{\n  "scripts": {\n    "build": "ttsc",\n    "start": "node dist/index.js"\n  }\n}

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Important: typia requires TypeScript version 4.4 or higher. The library will not work without the transformer.

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Quick Start with Code Example

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Let's create a simple example of user data validation.

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import typia from "typia";\n\n// Define the interface\ninterface IUser {\n  id: number;\n  name: string;\n  email: string;\n  age: number;\n  isActive: boolean;\n}\n\n// Create the validation function\nconst validateUser = typia.createValidate<IUser>();\n\n// Test data\nconst testData = {\n  id: 1,\n  name: "Ivan Petrov",\n  email: "ivan@example.com",\n  age: 30,\n  isActive: true,\n};\n\n// Validation\nconst result = validateUser(testData);\n\nif (result.success) {\n  console.log("Data is valid:", result.data);\n} else {\n  console.log("Validation error:", result.errors);\n}\n\n// Example with incorrect data\nconst badData = {\n  id: "not a number", // Should be number\n  name: "Ivan",\n  email: "not an email",\n  age: -5,\n  isActive: "yes", // Should be boolean\n};\n\nconst badResult = validateUser(badData);\nconsole.log("Errors:", badResult.errors);

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This example shows how easy it is to validate data using only a TypeScript interface. No additional schemas or decorators!

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Main Methods and Functions

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1. typia.