Write a Program to Find Plus One of an Array of Digits

# 66. Plus One

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 any leading 0’s.

Increment the large integer by one and return the resulting array of digits.

### Example 1:
```
Input: digits = [1,2,3]
Output: [1,2,4]
Explanation: The array represents the integer 123.
Incrementing by one gives 123 + 1 = 124.
Thus, the result should be [1,2,4].
```

### Example 2:
```
Input: digits = [4,3,2,1]
Output: [4,3,2,2]
Explanation: The array represents the integer 4321.
Incrementing by one gives 4321 + 1 = 4322.
Thus, the result should be [4,3,2,2].
 ```

Constraints:
```
1 <= digits.length <= 100
0 <= digits[i] <= 9
digits does not contain any leading 0's.
```

/**
 * @param {number[]} digits
 * @return {number[]}
 */
 var plusOne = function(digits) {
    for (let i = digits.length - 1; i >= 0; i--) {  
        digits[i]++;
        if (digits[i] > 9) {
            digits[i] = 0;
        } else {
            return digits;
        }
    }    
    digits.unshift(1);
    return digits;
};