#两个大数相加

function bignumAdd(s1, s2) {
  const n1 = s1.length;
  const n2 = s2.length;
  let temp = 0;
  let result = "";

  let i = n1 - 1;
  let j = n2 - 1;
  while (i >= 0 && j >= 0) {
    const res = Number(s1[i]) + Number(s2[j]);
    // temp = Math.floor((res + temp) / 10);
    if (res >= 10) {
      result = temp + res - 10 + result;
      temp = 1;
    } else {
      result = Number(temp + res) + result;
      temp = 0;
    }
    i--;
    j--;
  }

  while (i >= 0) {
    result = temp + Number(s1[i]) + result;
    i--;
  }

  while (j >= 0) {
    result = temp + Number(s2[j]) + result;
    j--;
  }

  return result;
}

console.log(bignumAdd("123456789", "123456789"));
// r:246913578
// r:246913578
// e:246813579
// e:357913578
// e:246813579
// console.log(bignumAdd('123', '12345'))