Function plusOne

javascript/0066-plus-one.js:7–13

(digits)

 * @return {number[]}
 */
var plusOne = (digits) => {
    add(digits);
    carry(digits); /* Time O(N) */
    addLeading(digits); /*           | Space O(N) */

    return digits;
};

var add = (digits) => (digits[digits.length - 1] += 1);