plus-one.js

// Given a non-empty array of digits representing a non-negative integer, plus one to the integer.
//
// The digits are stored such that the most significant digit is at the head of the list, and each element in the array contain a single digit.
//
// You may assume the integer does not contain any leading zero, except the number 0 itself.
//
// Example 1:
//
//
// Input: [1,2,3]
// Output: [1,2,4]
// Explanation: The array represents the integer 123.
//
//
// Example 2:
//
//
// Input: [4,3,2,1]
// Output: [4,3,2,2]
// Explanation: The array represents the integer 4321.
//
//


/**
 * @param {number[]} digits
 * @return {number[]}
 */
var plusOne = function(digits) {
    var i = digits.length - 1;
   while(i  >=  0)
   {
       if(digits[i] == 9)
       {
           digits[i] = 0;
           i--;
           // continue loop because we had to "carry" the 1
       }
       else 
       {
           digits[i] = digits[i] + 1;
           i--;
           break; // stop the while loop because no "carry" needed
       }
   }
   if(digits[0] === 0) {
       digits.unshift(1);
   }
   return digits;
};