JavaScript to TypeScript Converter (AI) — Free Online Tool

What is a JavaScript to TypeScript converter?

A JavaScript to TypeScript converter is a tool that automatically adds static type annotations to existing JavaScript code. It converts JS files to TS by inferring types from usage patterns and adding explicit type declarations, interfaces, and generics — turning plain .js files into fully typed .ts files.

How do I convert JavaScript to TypeScript?

To convert JavaScript to TypeScript: (1) Paste your JS code into the JS2TS converter. (2) Click Convert. (3) The AI adds type annotations, interfaces, and generics automatically. (4) Copy the TypeScript output. For manual conversion, rename .js to .ts and add type annotations by hand — but AI converters do this instantly.

Is this JS to TS converter free?

Yes, JS2TS is completely free. No account, login, or credit card required. Paste JavaScript code, click Convert, and copy the typed TypeScript output instantly — unlimited conversions.

What TypeScript patterns does the converter support?

The AI-powered JS to TS converter handles: function parameter and return types, object interfaces, array types, union and intersection types, generics, type inference, class definitions with typed properties, async/await return types, and module exports. It covers the most common JavaScript-to-TypeScript migration patterns.

Can I convert large JavaScript files?

Yes. JS2TS handles large files. For very large codebases, paste sections incrementally for best results. The converter processes any valid JavaScript including ES6+ syntax, CommonJS, and ESModules.

Does JS2TS store my code?

No. Conversions are processed in real time and your code is never stored or logged on our servers. Your JavaScript code stays private.

Why should I convert JS to TS?

Converting JavaScript to TypeScript adds compile-time error detection, better IDE autocomplete and refactoring, self-documenting code via type signatures, and safer team collaboration. TypeScript catches bugs before runtime — especially valuable in larger codebases.

What is the difference between JavaScript and TypeScript?

TypeScript is a superset of JavaScript that adds optional static typing. All valid JavaScript is valid TypeScript. TypeScript adds type annotations, interfaces, enums, and generics that are stripped at compile time — the output is plain JavaScript. The key benefit is catching type errors during development, not at runtime.