Simple xor two strings

xor.js

function xString(left, right) {
  let ret = '';
  let lStr = String(left);
  let rStr = String(right);
  if (lStr.length < rStr.length) {
    [lStr, rStr] = [rStr, lStr];
  }
  let len = lStr.length;
  rStr = rStr.padEnd(len, rStr);
  for (let i = 0; i < len; i++) {
    ret += String.fromCharCode(lStr.charCodeAt(i) ^ rStr.charCodeAt(i));
  }
  return ret;
}

// TEST CASE
let a = 'hello world';
let b = '123123';
let r = xString(a, b);
let ar = xString(a, r);
let ra = xString(r, a);
let br = xString(b, r);
let rb = xString(r, b);
console.log({ a, b, ab: r, ar, ra, br, rb });