Awesome

babel-plugin-flow-to-typescript

Babel plugin to convert Flow code into TypeScript

How to use

$ npm install -g @babel/cli @babel/core
$ npm install babel-plugin-flow-to-typescript

# you must use babel@^7.x.x
$ babel --version
7.4.4 (@babel/core 7.4.5)

$ babel --plugins babel-plugin-flow-to-typescript ${SRC_FLOW_FILE} -o ${DEST_TS_FILE}

Implementation status

Supported?	Syntax	Flow	TypeScript
✅	Maybe type	`let a:?number`	`let a: number \| null \| undefined`
✅	Void type	`void`	`void`
✅	Object type	`Object`	`object`
✅	Mixed type	`mixed`	`unknown`
✅	Function type	`(A, B) => C`	`(x1: A, x2: B) => C`
✅	Exact type	`{\| a: A \|}`	`{ a: A }`
✅	Indexers	`{ [A]: B }`	`{ [a: A]: B }`
✅	Existential type	`Map<, >`	`Map<any, any>`
✅	Opaque types	`opaque type A = B`	`type A = B`
✅	Variance	`interface A { +b: B, -c: C }`	`interface A { readonly b: B, c: C }`
✅	Type parameter bounds	`function f<A: string>(a:A){}`	`function f<A extends string>(a:A){}`
✅	Cast	`(a: A)`	`(a as A)`
✅	type/typeof import	`import type A from 'module'`	`import A from 'module'`
✅	$Keys	`$Keys<X>`	`keyof X`
✅	$Values	`$Values<X>`	`X[keyof X]`
✅	$ReadOnly	`$Readonly<X>`	`Readonly<X>`
✅	$Exact	`$Exact<X>`	`X`
✅	$Diff	`$Diff<X, Y>`	`Pick<X, Exclude<keyof X, keyof Y>>`
✅	$PropertyType	`$PropertyType<T, k>`	`T[k]`
✅	$ElementType	`$ElementType<T, k>`	`T[k]`
✅	$Shape	`$Shape<T>`	`Partial<T>`
✅	Class	`Class<T>`	`typeof T`
✅	typeof operator	`typeof foo`	`typeof foo`
✅	JSX	-	-
✅	Tuple type	`[number, string]`	`[number, string]`
✅	Type alias	`type A = string`	`type A = string`
✅	Flow Ignore	`$FlowFixMe`	`any`
✅	Interfaces	`interface X { +prop: string }`	`interface X { readonly prop: string }`
✅	Optional Members	`a?.b`	`...`
✅	Declare functions	`declare function x(false): true;`	`function x(x0: false): true;`
✅	Declare Class	`...`	`...`