JavaScript: Sum of the digits of a number

Last update on July 11 2025 13:03:24 (UTC/GMT +8 hours)

JavaScript Math: Exercise-68 with Solution

Sum of Digits

Write a JavaScript program to calculate the sum of a given number's digits.

In mathematics, the digit sum of a natural number in a given number base is the sum of all its digits. For example, the digit sum of the decimal number 6098 would be 6+0+9+8=23.

Sample Data:
6098 -> 23
-501 -> 6
2546 -> 17

Sample Solution-1:

JavaScript Code:

/**
 * Calculates the sum of digits of a given number.
 * @param {number} n - The input number.
 * @returns {number} - The sum of digits of the input number.
 */
function sum_Of_Digits(n) {
  // If the number is negative, convert it to positive
  if (n < 0) n = -n;
  // Initialize the result variable to store the sum of digits
  let result = 0;

  // Iterate through each digit of the number and add them to the result
  while (n > 0) {
    result += n % 10; // Add the last digit to the result
    n = Math.floor(n / 10); // Remove the last digit from the number
  }

  // Return the sum of digits
  return result;
}

// Test the function with different input numbers
console.log(sum_Of_Digits(6098)); // Output: 23
console.log(sum_Of_Digits(-501)); // Output: 6
console.log(sum_Of_Digits(2546)); // Output: 17

Output:

23
6
17

Flowchart:

$JavaScript Math flowchart of sum of the digits of a number$

Live Demo:

Sample Solution-2:

JavaScript Code:

/**
 * Calculates the sum of digits of a given number recursively.
 * @param {number} n - The input number.
 * @returns {number} - The sum of digits of the input number.
 */
function sum_Of_Digits(n) {
  // If the number is negative, convert it to positive
  if (n < 0) n = -n;
  
  // If the number has only one digit, return the number itself
  if (n < 10) return n;
  
  // Otherwise, recursively calculate the sum of digits
  return (n % 10) + sum_Of_Digits(Math.floor(n / 10));
}

// Test the function with different input numbers
console.log(sum_Of_Digits(6098)); // Output: 23
console.log(sum_Of_Digits(-501)); // Output: 6
console.log(sum_Of_Digits(2546)); // Output: 17
console.log(sum_Of_Digits(10));   // Output: 1
console.log(sum_Of_Digits(5));    // Output: 5

Output:

Flowchart:

$JavaScript Math flowchart of sum of the digits of a number$

Live Demo:

For more Practice: Solve these Related Problems:

Write a JavaScript function that calculates the sum of the digits of a number by converting it to a string and iterating over each character.
Write a JavaScript function that computes the sum of digits using arithmetic operations without converting the number to a string.
Write a JavaScript function that recursively calculates the digit sum and handles negative numbers by taking absolute values.
Write a JavaScript function that returns both the sum of the digits and the total number of digits present.

Go to:

PREV : Sum of Geometric Progression.
NEXT : Find All Primes Below N.

Improve this sample solution and post your code through Disqus.