封装一个计算两个数字的和和差的函数

  function getSum(a, b) {
            let he = a + b
            let cha = a - b
            return [he, cha]
        }
        let res = getSum(1, 3)
        console.log(`和为${res[0]}`);
        console.log(`差为${res[1]}`);