This is a simplified implementation of TypeScript's type system that's written in TypeScript's type annotations. This means that it uses types only — with no runtime code whatsoever.

You pass TypeScript code as a string to the TypeCheck generic and get possible type errors back (See the live demo):

☝ Please note that this project is meant to be used for fun and learning purposes and not for practical use.

See a live demo in your browser on the TypeScript Playground.

Alternatively, install @ronami/hypescript in your project with yarn or npm (TypeScript 4.7 or later is required):

yarn add @ronami/hypescript

Only a subset of TypeScript's syntax and features are available. Here's a list of examples (with browser demo links) for some code examples:

• Variables
• Functions
• Arrays
• Objects
• Methods
• Function return type
• Equality
• Arithmetic operations
• Global types

• TypeScripts Type System is Turing Complete
• Functions and algorithms implemented purely with TypeScript's type system
• Typing the Technical Interview in TypeScript
• A collection of TypeScript type challenges with online judge
• Extreme Explorations of TypeScript's Type System
• A SQL database implemented purely in TypeScript type annotations