Test1.js

const numbers = {
  "1": 1,
  "2": 2,
  "3": 3,
  "4": 4,
  "5": 5,
  "6": 6,
  "7": 7,
  "8": 8,
  "9": 9,
  "0": 0,
};

function add(str1, str2) {
  const num1 = str1.length >= str2.length ? str1 : str2;
  const num2 = str1.length < str2.length ? str1 : str2;

  let result = [];

  let carry = 0;
  let strToNum1 = 0;
  let strToNum2 = 0;
  let sum = 0;

  for (let i = num1.length - 1; i >= 0; i--) {
    strToNum1 = numbers[num1[i]];
    let diff = i - (num1.length - num2.length);
    strToNum2 = (diff >= 0 && diff < num2.length) ? numbers[num2[diff]] : 0;
    sum = strToNum1 + strToNum2 + carry;

    if (sum >= 10) {
      sum = sum - 10;
      carry = 1;
    } else {
      carry = 0;
    }
    result.push(sum);
  }
  if (carry === 1) {
    result.push(carry);
  }
  return result.reverse().join("");
}

const argList = process.argv.slice(2);

console.log(add(argList[0], argList[1]));