@flowtype

A typed dialect of JavaScript.

flow.org/
Joined November 2014
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12Media
Flow is now written in Rust 🦀 The migration from OCaml to Rust brought up to 2x faster type-checking on large codebases.
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Most of the Rust port was done by a single engineer over ~8 months, while the rest of the team kept shipping features: no code freeze. Read the full story: medium.com/flow-type/flows-o…

Flow’s OCaml to Rust Port

Flow’s OCaml codebase has been completely ported to Rust! Since v0.319 (released on June 17, 2026), our flow-bin npm package has been…

medium.com
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The Rust port is just the start. Flow in 2026 isn't like you remember: flow.org/

Flow: A Typed Dialect of JavaScript — JS Static Type Checker | Flow

Flow is a typed dialect of JavaScript — a static type system plus first-class language constructs, built for safety and scale.

flow.org
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Crashes at runtime - but TypeScript accepts it: zero errors under strict. Can you spot the bug?
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TypeScript lets you pass Array<string> where Array<string | Error> is expected, so the function pushes an Error to your string array. Flow rejects it. TS Playground, 0 errors: typescriptlang.org/play/?#co… Flow Playground, rejects with an error: flow.org/try/#1N4Igxg9gdgZgl…
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Flow catches the crash before you ship it. More examples where Flow is safer: flow.org/en/docs/flow-vs-typ…

Flow for TypeScript Users | Flow

Flow vs. TypeScript: how object exactness, variance defaults, `as` casts, type guards, and Flow's `component`/`hook`/`renders` syntax differ from TypeScript.

flow.org
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👀 Is this Flow, or TypeScript? Is Flow coming back? - Flow syntax aligns with TypeScript - Flow has pattern matching - Useful React hooks/component/renders syntax - Compiler has been recently ported to Rust I'll keep an eye on it for you, but this is promising!
Flow@flowtypeJun 9
JavaScript Pattern Matching with `match`, available now: medium.com/flow-type/javascr…

JavaScript Pattern Matching with Flow

No more switch! match expressions and statements bring exhaustiveness, destructuring, and readable branching together in one construct.

medium.com
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JavaScript Pattern Matching with `match`, available now: medium.com/flow-type/javascr…

JavaScript Pattern Matching with Flow

No more switch! match expressions and statements bring exhaustiveness, destructuring, and readable branching together in one construct.

medium.com
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If your "Flow vs TypeScript" take is from 2021, it's out of date. Flow looks like TypeScript now - but it has pattern matching and React component syntax, while catching runtime crashes TypeScript waves through. Examples below. 👇
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more replies
Another: TypeScript only validates the signature of a type-guard, not the body. Flow validates the body and rejects predicates that lie about what they check.
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Flow for TypeScript Users in 2026: 20+ side-by-side comparisons, verified against TypeScript 6.0.3 with 'strict' enabled: flow.org/en/docs/flow-vs-typ…

Flow for TypeScript Users | Flow

Flow vs. TypeScript: how object exactness, variance defaults, `as` casts, type guards, and Flow's `component`/`hook`/`renders` syntax differ from TypeScript.

flow.org
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SWC has added support for Flow: swc.rs/docs/usage/flow

Flow - SWC

SWC can parse Flow syntax and strip Flow type-only constructs during transform. This guide covers the most common ways to use Flow support: .swcrc@swc/core@swc/cli

swc.rs
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Flow now supports Mapped Types, inspired by TypeScript. Read more about them in our new blog post: medium.com/flow-type/announc…

Announcing: Mapped Types + Pick, Omit, and Record

tl;dr: Mapped types allow you to transform object types into other object types. We have added definitions for Pick, Omit, and Record…

medium.com
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youtu.be/HOFIefkepMA

Facebook wrote a language just for React (it's pretty cool)

I know Flow isn't exactly cool, but these changes absolutely are. T...

youtube.com
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The render types section of the blog post doesn't even go all that in depth. This is contrived for the sake of conciseness but really pay attention to what this code is expressing and understand how buck wild it is that we can express this with complete type safety!
Flow@flowtype3 Apr 2024
We added new language features to Flow for writing React. Learn about our new Component Syntax: medium.com/flow-type/announc…

New Flow Language Features for React

Write Safer and more Succinct React with Flow

medium.com
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We added new language features to Flow for writing React. Learn about our new Component Syntax: medium.com/flow-type/announc…

New Flow Language Features for React

Write Safer and more Succinct React with Flow

medium.com
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