#2544 - Alternating Digit Sum

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Problem Description

You are given a positive integer n. Each digit of n has a sign according to the following rules:

The most significant digit is assigned a positive sign.
Each other digit has an opposite sign to its adjacent digits.

Return the sum of all digits with their corresponding sign.

Solution

/**
 * @param {number} n
 * @return {number}
 */
var alternateDigitSum = function(n) {
  let sum = 0;
  let isPositive = true;

  while (n > 0) {
    const digit = n % 10;
    sum += isPositive ? digit : -digit;
    isPositive = !isPositive;
    n = Math.floor(n / 10);
  }

  return isPositive ? -sum : sum;
};