test1

test1.js

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

sumTwoNum(args[0], args[1])

function sumTwoNum(str1, str2) {
  if (str1.length > str2.length) {
    [str1, str2] = [str2, str1]
  } 

  let str = ""
  let n1 = str1.length, n2 = str2.length;
  str1 = str1.split("").reverse().join("");
  str2 = str2.split("").reverse().join("");

  let carry = 0;

  for (let i = 0; i < n1; i++) {
    let sum = ((str1[i].charCodeAt(0) - '0'.charCodeAt(0)) + (str2[i].charCodeAt(0) - '0'.charCodeAt(0)) + carry);
    str += String.fromCharCode(sum % 10 + '0'.charCodeAt(0));
    carry = Math.floor(sum / 10);
  }

  for (let i = n1; i < n2; i++) {
    let sum = ((str2[i].charCodeAt(0) - '0'.charCodeAt(0)) + carry);
    str += String.fromCharCode(sum % 10 + '0'.charCodeAt(0));
    carry = Math.floor(sum / 10);
  }

  if (carry > 0) {
    str += String.fromCharCode(carry + '0'.charCodeAt(0));
  }

  str = str.split("").reverse().join("");

  console.log(str);
  return str;
}