Callback function from map() always returns same output

November 22, 2021

I am counting the number of divisors for every number in the list and wrote a separate function which works fine on its own. But when I use the function as a callback to map(), it fails miserably, always returning 1.

let list = [641, 976, 517, 263, 136, 270, 941, 
    400, 915, 790, 539, 414, 816, 546, 675,548, 299,
    812, 45, 432, 392, 178, 310, 439, 956, 319, 450,
    566, 72, 74, 715, 336, 723, 854, 472, 996, 604, 
    861, 182, 609, 117, 484, 358, 1000, 363, 237, 
    111, 629, 759, 505, 510];
 
list.map(num => countDivisors(num))
 
function countDivisors(n) {
  let numberOfDivisors = 0;

  for (let i = 1; i <= n; i++) {
    if (n % i == 0) {
      numberOfDivisors++;
    }
    return numberOfDivisors;
  }
}

How can this be fixed?

>Solution :

You are returning in the for-loop, you should return the result before the function ends and after the loop as:

You can also pass function as

list.map(countDivisors);

There is no need to take num as input and then pass the num to countDivisors

let list = [
  641, 976, 517, 263, 136, 270, 941, 400, 915, 790, 539, 414, 816, 546, 675,
  548, 299, 812, 45, 432, 392, 178, 310, 439, 956, 319, 450, 566, 72, 74, 715,
  336, 723, 854, 472, 996, 604, 861, 182, 609, 117, 484, 358, 1000, 363, 237,
  111, 629, 759, 505, 510,
];

list.map((num) => countDivisors(num));

function countDivisors(n) {
  let numberOfDivisors = 0;

  for (let i = 1; i <= n; i++) {
    if (n % i == 0) {
      numberOfDivisors++;
    }
  }
  return numberOfDivisors;
}