Given an array of positive integers nums, return an array answer that consists of the digits of each integer in nums after separating them in the same order they appear in nums. To separate the digits of an integer is to get all the digits it has in

separateDigits.js

/**
 * @param {number[]} nums
 * @return {number[]}
 */
var separateDigits = function(nums) {
    const res = [];

    for (let n of nums) {
        // If the number is a single digit, just append it
        if (n < 10) {
            res.push(n);
            continue;
        }

        const stack = [];

        // Extract digits from right to left using modulo/division
        while (n > 0) {
            stack.push(n % 10);
            n = Math.floor(n / 10);
        }

        // Digits were collected in reverse order, so pop to restore left->right
        while (stack.length) {
            res.push(stack.pop());
        }
    }

    return res;
};