Flow to Plain JavaScript Converter
Paste Flow-annotated source to instantly strip out its type annotations and produce plain, runnable JavaScript using Babel's Flow parser. Free online developer tool.
Paste Flow Source
Plain JavaScript
Plain JavaScript output will appear here...
Free Flow to Plain JavaScript Converter
Paste Flow-annotated source to instantly strip out its type annotations and produce plain, runnable JavaScript — using Babel's official Flow parser to remove every type construct, the same parsing approach Flow projects have relied on for production builds for years.
How to Use It
Paste any Flow-annotated source into the input box, or click "Load Example." The tool parses your code with Babel's Flow syntax plugin, walks the resulting syntax tree removing every Flow-only construct — type annotations, type aliases, interfaces, type-only imports/exports, and runtime type casts — and regenerates the remaining code, leaving your actual runtime logic completely untouched.
Example
Given a function greet(name: string, address: Address): string declaration with a Flow type Address alias above it, the tool emits the plainfunction greet(name, address) version with the type alias removed entirely — the function body is unchanged.
Common Use Cases
- Running a Flow-typed snippet in a plain JavaScript environment without a build step.
- Migrating a codebase off Flow by first producing a runnable, type-free baseline.
- Quickly checking what a Flow-annotated file looks like once its types are removed.
FAQs
Is this an approximation, or does it produce exact output?
The logic is exact — every Flow type construct is removed via the same battle-tested Flow-parsing approach used across the JavaScript ecosystem, not a regex or a hand-written approximation. One honest caveat: the output is regenerated from the parsed syntax tree rather than a minimal patch of your original text, so formatting details like quote style or spacing can differ from your input even though the runtime behavior is identical.
Does this type-check my code first?
No — it only removes type syntax; it doesn't verify that your Flow types were correct in the first place. If you need type-checking, run your code through the Flow compiler itself before using this tool.
Is my code uploaded anywhere?
No — type removal happens entirely client-side in your browser, using Babel's parser loaded on demand. Nothing you paste is sent to a server.