CODEWITHSUNDEEP
javascriptflowtype
Ferry
Ferry

Reputation: 340

Flow type for function that return function

From flow's function type docs, function that return primitive type is like this

const a = aFunc = (id: number): number => id + 1.

But, how to create flow type for a function that return a function?

const aFunc = (id: number): <what type?> => {
  return bFunc(a): void => console.log(a)
}

Upvotes: 6

Views: 3758

Answers (1)

MichaelDeBoey
MichaelDeBoey

Reputation: 2385

You can either create a separate type, or you can do it inline.
Or you can choose to don't specify a return-type at all, because flow knows the return type of bFunc.

const bFunc = (a): void => console.log(a);

Separate type: 

type aFuncReturnType = () => void;
const aFunc = (id: number): aFuncReturnType => () => bFunc(id);

Inline: 

const aFunc = (id: number): (() => void) => () => bFunc(id);

You can also see this on flow.org/try 🙂

Upvotes: 7

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