Support
A contact page is linked from the site for questions, alongside a blog and extensive guides and cheatsheets.
Learn moreJS2TS
AI converter that turns plain JavaScript into typed TypeScript in seconds
Intermediate
What is JS2TS?
JS2TS is a free, no login web converter that uses AI to rewrite JavaScript as TypeScript, complete with inferred types, interfaces and generics. It also bundles converters for JSON, YAML, XML, CSV, Zod, OpenAPI, Tailwind and JSX, plus cheatsheets and guides for developers.
JS2TS is a browser based converter that takes JavaScript source code and returns TypeScript with type annotations, interfaces and generics. The workflow is deliberately minimal: paste or type JavaScript into the input panel, press Convert, and read the typed result in the output panel beside it. A sample code button lets a newcomer see the transformation before committing their own file, and the site states plainly that no login is needed for the core conversion. The tool targets developers sitting on untyped JavaScript who want a typed starting point rather than a hand written rewrite. The site frames the alternative as hours of manual work on a single large file: renaming extensions from .js to .ts, then annotating every variable, parameter and return value. JS2TS positions the AI pass as a way to collapse that into seconds, and its example (a greet function gaining a string parameter and string return type) shows the expected shape of the output. JS2TS is more than one converter. The same interface hosts adjacent utilities: JSON to TypeScript, TypeScript to JavaScript, TypeScript to Zod, OpenAPI to TypeScript, JSON to Zod, JSON to JSON Schema, YAML, XML and CSV to JSON, CSS to Tailwind and the reverse, HTML to JSX, JSX to TSX and JS to TSX. That breadth makes it a practical stop for migration chores that usually get scattered across several tabs, and the reference material (TypeScript, Zod and Tailwind cheatsheets, guides on generics, utility types, strict mode and React usage, plus comparison articles) supports the tools rather than standing alone. Alternatives fall into two camps. Editor plugins and type inference helpers work inside a codebase and respect project configuration; JS2TS does not claim that, working on pasted snippets instead. General purpose chatbot assistants can attempt the same conversion but give no fixed output panel or nearby cheatsheets. JS2TS occupies the quick, single file niche between them, best used to produce a typed draft that a developer then reviews against real runtime data.
How do you use JS2TS?
1Open the JavaScript to TypeScript converter
Load the JS2TS homepage, where the converter sits at the top with a JavaScript input panel on the left and a TypeScript output panel on the right.2Paste or type your JavaScript
Drop your code into the input box, either typing it directly or copying it from your editor. Start with a single function or file rather than a whole project.3Try the sample first if you are unsure
Use the Try Sample Code option to load a demo snippet and see how the converter annotates types before you commit your own source.4Run the conversion
Press Convert and read the TypeScript in the output panel, checking that parameters, return values and object shapes carry the types you expect.5Read the migration guide and patch the result
Work through the how to convert guide for project level steps such as renaming files and enabling strict mode, then reconcile any inferred types with your actual data.6Reach for a neighbouring converter when needed
If your typed code needs runtime validation or your data is JSON, run the same paste and convert flow on the TypeScript to Zod or JSON to TypeScript pages.
Pros and cons
Pros
- Paste and convert workflow with an output panel, sample code and no login prompt for the main converterAI
- Beyond JS to TS, includes JSON, YAML, XML, CSV, Zod, OpenAPI, Tailwind and JSX converters in one placeAI
- Reference library of TypeScript, Zod and Tailwind cheatsheets plus generics, strict mode and React guidesAI
- Sample conversion on the homepage shows exactly what typed output to expect before pasting real codeAI
- Free to use according to the site, which lowers the cost of trying it on a legacy fileAI
Cons
- Works on pasted snippets, so large multi file projects and imports must be handled piece by pieceAI
- No stated guarantees about how inferred types are validated against real runtime data, so output needs reviewAI
- The AI model behind the conversion and its handling of pasted proprietary code are not explained on the homepageAI
- Breadth of unrelated utilities risks a less polished tool than a dedicated TypeScript migration productAI
How much does JS2TS cost?
Features
AI conversion of JavaScript to TypeScript with inferred types, interfaces and generics, plus separate converters for JSON to TypeScript, TypeScript to JavaScript and Zod, OpenAPI to TypeScript, JSON to Zod and JSON Schema, YAML, XML, CSV and JS objects to JSON, CSS to Tailwind and back, and HTML to JSX, JSX to TSX and JS to TSX. Cheatsheets, guides and comparison articles accompany the tools.
Frequently asked questions about JS2TS
How do you use JS2TS?
The walkthrough on this page covers 6 steps: 1. Open the JavaScript to TypeScript converter 2. Paste or type your JavaScript 3. Try the sample first if you are unsure 4. Run the conversion 5. Read the migration guide and patch the result 6. Reach for a neighbouring converter when needed.What platforms does JS2TS support?
JS2TS is available on Web App.What are the limitations of JS2TS?
Works on pasted snippets, so large multi file projects and imports must be handled piece by piece. No stated guarantees about how inferred types are validated against real runtime data, so output needs review. The AI model behind the conversion and its handling of pasted proprietary code are not explained on the homepage.
Status
StatusActive
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Added10/21/2026
Platforms
Web App
Pricing
Free
