JavaScriptConverter vs js2ts
Two ways to convert JavaScript to TypeScript. One uses deterministic AST transforms, the other sends your code to a cloud LLM. Here's an honest side-by-side.
| Feature | JavaScriptConverter | js2ts.com |
|---|---|---|
| Conversion engine | Deterministic AST (ts-morph) | Cloud LLM (AI) |
| Output reproducibility | Same input → same output | Varies between runs |
| Type hallucinations | Impossible by design | Possible |
| Offline / local conversion | Free Windows desktop app | No — cloud only |
| Code sent to server | Online: yes · Desktop: never | Always |
| Batch (folder / ZIP) conversion | Yes | Single file paste |
| Per-file diagnostics | Yes — every transform reported | Limited |
| JSDoc → TypeScript types | Yes | Inferred by LLM |
| CommonJS → ESM rewriting | Yes | Yes |
| Class field detection | Yes — lifted into class body with types | LLM-dependent |
| tsconfig.json generation | Yes | No |
| Free tier | 5 files / 1 MB online · unlimited desktop | Credit-limited |
| Adjacent converters | JSON→TS, TS→Zod, JSDoc→TS | JSON→TS, OpenAPI→TS, TS→Zod |
When to pick JavaScriptConverter
- • You need predictable, reviewable output — same input, same TypeScript, every time.
- • Your source code is sensitive and can't leave your machine — use the free desktop app.
- • You're converting an entire project and want a file-tree picker plus diagnostics, not a paste box.
- • You want a generated tsconfig.json alongside the converted files.
When to pick js2ts
- • You're converting a tiny snippet and want creative type-name suggestions that an LLM may produce.
- • You need access to a wider matrix of adjacent converters in one place.
- • You don't mind cloud processing and non-deterministic output.
The deterministic vs LLM trade-off
LLM-based converters can produce plausible-looking output that doesn't match the original program's semantics. They can invent fields, mistype optional parameters, or rewrite control flow under the hood. For toy snippets that's fine. For production code that's a code-review tax on every conversion.
JavaScriptConverter's engine runs on top of the TypeScript compiler. The transforms it
performs are explicit and documented: require() rewriting,
JSDoc extraction, class-field detection, static-member hoisting, accessibility inference,
tsconfig generation, error-suppression scaffolding. Nothing more. The diff stays auditable.
Try it yourself
Paste the same code into both tools. Compare the output, the type accuracy, and the diagnostics.
Comparison is based on publicly documented features of js2ts.com at the time of writing. Vendor descriptions may change; verify on each vendor's site before relying on capability claims.
