JavaScript实现大整数加法

实现大整数加法

即两个数字字符相加，采用按位加法实现

方法

const add = (a, b) => {
  let i = a.length - 1;
  let j = b.length - 1;

  let carry = 0;
  let ret = "";
  while (i >= 0 || j >= 0) {
    let x = 0;
    let y = 0;
    let sum = "";

    if (i >= 0) {
      x = a[i] - "0";
      i--;
    }

    if (j >= 0) {
      y = b[j] - "0";
      j--;
    }

    sum = x + y + carry;

    if (sum >= 10) {
      carry = 1;
      sum -= 10;
    } else {
      carry = 0;
    }

    ret = sum + ret;
  }

  if (carry) {
    ret = carry + ret;
  }

  return ret;
};

export default add;

// add('99999999999999', '1');
// add('1', '99999999999999');
// add('1234', '4321');