Sum of Digits

Problem Statement

Solution 1: Using a Loop

function sumOfDigitsLoop(posNum) {
  if (typeof posNum !== "number" || Number.isNaN(posNum)) {
    throw new Error("Input must be a number");
  }

  // Convert the number to its absolute value and remove the decimal point
  posNum = Math.abs(posNum).toString().replace('.', '');
  let sum = 0;

  for (let i = 0; i < posNum.length; i++) {
    sum += parseInt(posNum[i], 10);
  }

  return sum;
} 

const n1 = 54;
sumOfDigitsLoop(n1);  //output: 9 

const n2 = -1234;
sumOfDigitsLoop(n2);  //output: 10 

Solution 2: Using Array Methods

function sumOfDigitsArray(posNum) {
  if (typeof posNum !== "number" || Number.isNaN(posNum)) {
    throw new Error("Input must be a number");
  }

  // Convert the number to its absolute value and remove the decimal point
  posNum = Math.abs(posNum).toString().replace('.', '');
  return posNum
    .split("")
    .map((digit) => parseInt(digit, 10))
    .reduce((acc, val) => acc + val, 0);
} 

const n1 = 54;
sumOfDigitsArray(n1);  //output: 9 

const n2 = -1234;
sumOfDigitsArray(n2);  //output: 10 

Solution 3: Using Recursion

function sumOfDigitsRecursion(posNum) {
  // Ensure input is a number and not NaN
  if (typeof posNum !== "number" || Number.isNaN(posNum)) {
    throw new Error("Input must be a valid number");
  }

  // Convert the number to its absolute value and remove the decimal point
  posNum = Math.abs(posNum).toString().replace('.', '');

  // Define the recursive function to sum digits
  const sumDigits = (str) => {
    if (str.length === 0) {
      return 0;
    }
    return parseInt(str[0], 10) + sumDigits(str.slice(1));
  };

  return sumDigits(posNum);
} 

const n1 = 54;
sumOfDigitsRecursion(n1);  //output: 9 

const n2 = -1234;
sumOfDigitsRecursion(n2);  //output: 10 

Solution 4: Using Mathematical Operations

function sumOfDigitsMath(posNum) {
  if (typeof posNum !== "number" || Number.isNaN(posNum)) {
    throw new Error("Input must be a number");
  }

  posNum = Math.abs(posNum); // Handle negative numbers
  posNum = parseInt(posNum.toString().replace('.', ''), 10); // Remove decimal point
  let sum = 0;

  while (posNum > 0) {
    sum += posNum % 10;
    posNum = Math.floor(posNum / 10);
  }

  return sum;
} 

const n1 = 54;
sumOfDigitsMath(n1);  //output: 9 

const n2 = -1234;
sumOfDigitsMath(n2);  //output: 10 

Solution 5: Using String.prototype.split and Array.prototype.reduce

function sumOfDigitsSplitReduce(num) {
  if (typeof num !== "number" || Number.isNaN(num)) {
    throw new Error("Input must be a number");
  }

  // Convert the number to its absolute value and remove the decimal point
  const numberStr = Math.abs(num).toString().replace('.', '');

  // Split the string into characters and sum the numeric values
  return numberStr
    .split("")
    .reduce((sum, char) => sum + Number(char), 0);
} 

const n1 = 54;
sumOfDigitsSplitReduce(n1);  //output: 9 

const n2 = -1234;
sumOfDigitsSplitReduce(n2);  //output: 10 

Solution 6: Using Array.from

function sumOfDigitsArrayFrom(num) {
  if (typeof num !== "number" || Number.isNaN(num)) {
    throw new Error("Input must be a number");
  }

  // Convert the number to its absolute value and remove the decimal point
  const numberStr = Math.abs(num).toString().replace('.', '');

  // Convert the string to an array of digits and sum them
  return Array.from(numberStr).reduce((sum, char) => {
    // Only add if the character is a digit
    return sum + (parseInt(char, 10) || 0);
  }, 0);
} 

const n1 = 54;
sumOfDigitsArrayFrom(n1);  //output: 9 

const n2 = -1234;
sumOfDigitsArrayFrom(n2);  //output: 10 

Solution 7: Handling Floating Points and Edge Cases

function sumOfDigitsRecursionFloat(posNum) {
  if (typeof posNum !== "number" || Number.isNaN(posNum)) {
    throw new Error("Input must be a number");
  }

  // Convert the number to its absolute value and remove the decimal point
  const numberStr = Math.abs(posNum).toString().replace('.', '');
  
  // Call the recursion function with the cleaned-up string representation
  return sumOfDigitsRecursion(Number(numberStr));
} 

const n1 = 54;
sumOfDigitsRecursionFloat(n1);  //output: 9 

const n2 = -1234;
sumOfDigitsRecursionFloat(n2);  //output: 10 

Solution 8: Using a while loop

function sumOfDigitsWhileLoop(posNum) {
  if (typeof posNum !== "number" || Number.isNaN(posNum)) {
    throw new Error("Input must be a number");
  }

  // Convert the number to its absolute value and remove the decimal point
  posNum = Math.abs(posNum).toString().replace('.', '');
  posNum = parseInt(posNum, 10); // Ensure it's an integer
  let sum = 0;

  while (posNum > 0) {
    sum += posNum % 10;
    posNum = Math.floor(posNum / 10);
  }

  return sum;
} 

const n1 = 54;
sumOfDigitsWhileLoop(n1);  //output: 9 

const n2 = -1234;
sumOfDigitsWhileLoop(n2);  //output: 10 

Resources

Wikipedia

More Problems Solutions