进阶版 JS 大数相加

• 实现整数相加
• 实现浮点数相加
• 实现多数相加

代码已经通过 LeetCode 检测通过，感觉还是有很多可以优化的空间，还烦请留言赐教，谢谢。

function bigNumberAddition() {
  
  function cutNumberByDot(_n) {
    const n = String(_n);
    return n.split('.');
  }
  
  function addition(n1, n2) {
    const [n1_integer, n1_float] = cutNumberByDot(n1);
    const [n2_integer, n2_float] = cutNumberByDot(n2);
    let plusOne = 0;
    let float = '';
    
    if (n1_float && n2_float) {
      let shortNumber = n1_float.length > n2_float.length ? n2_float : n1_float;
      const longNumber = n1_float.length < n2_float.length ? n2_float : n1_float;
      for (let i = 0; i < longNumber.length; i++) {
        if (!shortNumber[i]) {
          shortNumber += '0';
        }
      }
      float = integerAddition(shortNumber, longNumber);
      if (float.length > longNumber.length) {
        plusOne = 1;
        float = float.substr(1);
      }
    } else if (n1_float || n2_float) {
      float = (n1_float || n2_float);
    }
    
    let integer = integerAddition(n1_integer, n2_integer, plusOne);
    
    let ret;
    if (n1_float || n2_float) {
      ret = integer + '.' + float;
    } else {
      ret = integer;
    }
    return ret;
  }
  
  function integerAddition() {
    // 记得给参数转字符串
    const args = [...arguments].map((arg) => typeof (arg) !== "string" ? String(arg) : arg);
    return args.reduce((s1 = '0', s2 = '0') => {
      let s1index = s1.length - 1;
      let s2index = s2.length - 1;
      let plusOne = 0;
      let ret = '';
      while (s1index >= 0 || s2index >= 0) {
        const sum = +(s1[s1index] ?? 0) + +(s2[s2index] ?? 0) + plusOne;
        if (sum >= 10) {
          ret = sum % 10 + ret;
          plusOne = 1;
        } else {
          ret = sum + ret;
          plusOne = 0;
        }
        s1index--;
        s2index--;
      }
      // 记得最后还要判断一下是否还需要再加一位 1 在结果的前面
      return plusOne ? plusOne + ret : ret;
    })
  }
  
  const args = [...arguments];
  return args.reduce((prev, next) => addition(prev, next));
}