Function returning NaN?

Question

Hello friends
I did an example for the first class function topic
I did a function called calcAge that gets the user's date of birth and calculates the user's age, and using the first class function, the checkAge function gets the age calculation, but whatever I do, the second function gets the first function as an argument. Has returned the value of NaN

const calcAge = (brithDay) => {
const ageResult = 2021 - brithDay;
return ageResult
}

console.log(calcAge(1992))

const checkAge = (age) => {

return age()

}

console.log(checkAge(calcAge))

Answer 1

while calling the function calcAge, u didnt pass any arguments.
the birthDay value is null;

const calcAge = (brithDay) => {
const ageResult = 2021 - brithDay;
return ageResult
}

console.log(calcAge(1992))

const checkAge = (age, args) => {

return age(args)

}

console.log(checkAge(calcAge, 1999))