swap-without-third-variable.js

function swapWithoutThirdVariable({ firstNo, secondNo }) {
  // if either of two input numbers don't pass as integers, return error
  if (!Number.isInteger(firstNo) || !Number.isInteger(secondNo)) {
    return 'Please input two integers for both "firstNo" and "secondNo"'
  }

  // first number is sum of two numbers
  firstNo = firstNo + secondNo

  // get first number again afer subtracting the second number from sum (firstNo)
  secondNo = firstNo - secondNo

  // get second number after subtracting the first number (secondNo) from sum (firstNo)
  firstNo = firstNo - secondNo

  return {
    firstNoAfterSwap: firstNo,
    secondNoAfterSwap: secondNo
  }
}

console.log(swapWithoutThirdVariable({ firstNo: 10, secondNo: 2 }))