数字特别大的时候，大数计算如何实现

　　添加图片注释，不超过 140 字（可选） 方式一const add = (num1, num2) => {     // 获取最大长度     const len = Math.max(num1.length, num2.length);     // 补0     num1 = num1.padStart(len, 0);     num2 = num2.padStart(len, 0);        let flag = 0,esult = ``,temp = 0;     for(let i=len-1; i>=0;  i--){       temp = flag + parseInt(num1[i]) + parseInt(num2[i])       result = (temp%10) + result        flag = parseInt(temp/10)     }     // 判断是否进位     return result = (flag === 1 ? ＂1＂ : ＂＂) + result; }   const n1 = ＂9007199254740990＂ const n2 = ＂1229007199254740993443＂  add(n1, n2);  // ＂1229016206453995734433＂方式二let n1 = BigInt(＂111111111111111111111111111111111111111＂) let n2 = 222222222222222222222222222222222222222n  console.log(n1 + n2, n1 * n2, n1 - n2);方式三var addStrings = function(num1, num2) {   if (+num1 === 0) return num2   if (+num2 === 0) return num1   const arr1 = num1.split(＂＂)   const arr2 = num2.split(＂＂)   let res = ＂＂   let flag = 0   while (arr1.length || arr2.length || flag) {     const a = arr1.length ? +arr1.pop() : 0     const b = arr2.length ? +arr2.pop() : 0     const s = a + b + flag     const t = s % 10     flag = s >= 10 ? 1 : 0     res = t + res   }   return res };方式四function addStrings(num1: string, num2: string): string {   let i = num1.length - 1, j = num2.length - 1, add = 0;   const ans: number[] = [];    while(i >= 0 || j >= 0 || add!= 0) {     const x = i >= 0 ? Number.parseInt(num1.charAt(i), 10) : 0;     const y = j >= 0 ? Number.parseInt(num2.charAt(j), 10) : 0;     const r = x + y + add;     ans.unshift(r % 10);     add = Math.floor(r / 10);     i -= 1;     j -= 1;   }    return ans.join(＂＂); };方式五var addStrings = function (num1, num2) {   let aLen = num1.length - 1;   let bLen = num2.length - 1;   let remainder = 0;   let result = [];   while (aLen >= 0 || bLen >= 0 || remainder !== 0) { // 注意最后一个进位     const a = aLen >= 0 ? num1.charAt(aLen) - ＂0＂ : 0;     const b = bLen >= 0 ? num2.charAt(bLen) - ＂0＂ : 0;     const tempResult = a + b + remainder;     result.push((tempResult) % 10);     remainder = Math.floor(tempResult / 10);     aLen -= 1;     bLen -= 1;   }   return result.reverse().join(＂＂); };