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Javascript – How do I type an array of CallableFunction's that might be async?

I have this code:

export const provide = async (callables: CallableFunction[]) => {
    for (const callable of callables) {
        await callable()
    }
}

A callable may or may not be async.

I’ve tried typing it like this:

export const provide = async (callables: CallableFunction[] | Promise<CallableFunction>[]) => {
    for (const callable of callables) {
        await callable()
    }
}

But vscode gives me the error:

This expression is not callable.
No constituent of type ‘CallableFunction | Promise’ is callable.

How do I type an array of CallableFunction’s that may or may not be async?

Tags:

2

Answers


  1. 0

    CallableFunction includes any would-be async functions –

    const provide = async (callables: CallableFunction[]) => {
    for (const callable of callables) {
        await callable()
    }
}

    provide([
    () => { console.log("hello") },
    async () => { 
        await new Promise(r => setTimeout(r, 1000))
        console.log("world")
    },
])

    hello
world

    typescript playground

    Thank you @JaromandaX for the discussion.

    Login or Signup to reply.
  2. 0

    Generally, instead of typing functions with CallableFunction, we type them like this: ((...) => ...) as you can see in the typescript documentation: https://www.typescriptlang.org/docs/handbook/2/functions.html#function-type-expressions

    Since asynchronous functions return a Promise, the type "any" will fit for them too.

    This is how you can fix it:

    export const provide = async (callables: (() => any)[]) => {
    for (const callable of callables) {
        await callable()
    }
}
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