You are given a 0-indexed integer array nums, where nums[i] is a digit between 0 and 9 (inclusive). The triangular sum of nums is the value of the only element present in nums after the following process terminates: Let nums comprise of n elements.

triangularSum.js

/**
 * @param {number[]} nums
 * @return {number}
 */
var triangularSum = function(nums) {
    // Continue the process until only one element remains
    while (nums.length > 1) {
        let newNums = [];
        // Generate the next row by summing adjacent elements modulo 10
        for (let i = 0; i < nums.length - 1; i++) {
            newNums.push((nums[i] + nums[i + 1]) % 10);
        }
        // Replace nums with the new row
        nums = newNums;
    }
    // Return the final remaining element
    return nums[0];
};