Is it possible to attach a nested function to a parameter of the parent function in JavaScript?

Question

Is it possible to attach a nested function to a parameter of the parent function in JavaScript?

Here's a query that might appear basic and straightforward. It could even be a repeated question, as I struggled to use the correct keywords in my search.

The puzzle seems to lie in why this code snippet functions correctly:

let rAMessage = 'Ride along, everyone!'

let messageNum = 5

function computeNumber() {
      return 5+5
    }

function RideAlong(message, number = computeNumber()) {
    alert(`${message} + ${number}`)
}

RideAlong(rAMessage)

However, this alternate version doesn't produce the desired outcome:

let rAMessage = 'Ride along, everyone!'

let messageNum = 5

function RideAlong(message, number = computeNumber()) {
    function computeNumber() {
      return 5+5
    }
    alert(`${message} + ${number}`)
}

RideAlong(rAMessage)

Is there a possible solution to make it functional?

javascript function

Answer 1

Answer №1

The desired functionality of the second function is not entirely clear. However, it appears that you intend to allow for a number argument with the default value being the result of computeNumber, which is not defined outside the function. To achieve this, it would be advisable to compute the default value within the function itself:

let welcomeMessage = 'Welcome aboard everyone!'

function WelcomeAboard(message, number) {
    function computeNumber() {
      return 6 + 4
    }
    if (number === undefined) number = computeNumber()
    console.log(`${message} + ${number}`)
}

WelcomeAboard(welcomeMessage)

WelcomeAboard(welcomeMessage, 3)

Answer 2

The desired functionality of the second function is not entirely clear. However, it appears that you intend to allow for a number argument with the default value being the result of computeNumber, which is not defined outside the function. To achieve this, it would be advisable to compute the default value within the function itself:

let welcomeMessage = 'Welcome aboard everyone!'

function WelcomeAboard(message, number) {
    function computeNumber() {
      return 6 + 4
    }
    if (number === undefined) number = computeNumber()
    console.log(`${message} + ${number}`)
}

WelcomeAboard(welcomeMessage)

WelcomeAboard(welcomeMessage, 3)

Is it possible to attach a nested function to a parameter of the parent function in JavaScript?

Answer №1

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