You are given a large integer represented as an integer array digits, where each digits[i] is the ith digit of the integer. The digits are ordered from most significant to least significant in left-to-right order. The large integer does not contain a

plusOne.js

/**
 * @param {number[]} digits
 * @return {number[]}
 */
var plusOne = function(digits) {
    // Start from the last digit and move left
    for (let i = digits.length - 1; i >= 0; i--) {

        // If the current digit is less than 9, we can safely increment it
        // and return immediately because no carry is needed.
        if (digits[i] < 9) {
            digits[i]++;        // simple increment
            return digits;      // done - no ripple effect
        }

        // If the digit is 9, it becomes 0 and we carry 1 to the next digit.
        digits[i] = 0;
    }

    // If we exit the loop, it means all digits were 9.
    // Example: [9,9,9] -> [0,0,0] at this point.
    // We need to add a new leading 1.
    digits.unshift(1);

    return digits;
};