Flow-to-TypeScript

Compile Flow files to TypeScript

In Pre-Alpha - contributions welcome.

Installation

# Using Yarn:
yarn add flow-to-typescript

Or, using NPM:
npm install flow-to-typescript --save

Usage

CLI

# Install globally
yarn global add flow-to-typescript

Compile a file (all of these are equivalent)
flow2ts my/file.js.flow
flow2ts my/file.js.flow my/file.ts
flow2ts my/file.js.flow > my/file.ts
flow2ts -i my/file.js.flow -o my/file.ts
flow2ts --input my/file.js.flow --output my/file.ts

Programmatic

import { compile } from 'flow-to-typescript'
import { readFileSync, writeFileSync } from 'fs'

let path = 'path/to/file.js.flow'
let file = readFileSync(path, 'utf-8')
compile(file, path).then(ts =>
  writeFileSync('path/to/file.ts', ts)
)

TypeScript vs. Flow

Features

| Done? | | Flow | TypeScript | |-------|-------------|-----------------------------------------|------------| | ✅ | Maybe |

?type

type \| null \| undefined

null

null

typeof undefined

undefined

mixed

unknown

void

void

(A, B) => C

(a: A, b: B) => C

(a: A, b: B) => %checks

(a: A, b: B) => C

(a: A, b: B) => C %checks

(a: A, b: B) => C

{\| a: A \|}

{ a: A }

{ [A]: B }

{ [a: A]: B }

opaque type A = B

type A = B

interface A { +b: B, -c: C }

interface A { readonly b: B, c: C }

(a: A)

(a as A)

import type A from './b'

import A from './b'

import type { A } from './b'

import { A } from './b'

Utilities

| Done? | | Flow | TypeScript | |-------|-------------|-----------------------------------------|------------| | | Keys |

$Keys

keyof A

$Values

A[keyof A]

$ReadOnly

Readonly

$Exact

A

$Diff

|
|       | Rest        |

|

|
|       | Property type |

|

|
|       | Element type |

|

|
|       | Dependent type |

| TODO |
|       | Mapped tuple |

| TODO |
|       | Return type |

|

|
|       | Class       |

|

|
|       | Supertype   |

|

(warn - vote for https://github.com/Microsoft/TypeScript/issues/14520) |
|       | Subtype     |

|

|
|       | Existential type |

|