题解 | 求四位数各个数位之和

const rl = require('readline').createInterface({input: process.stdin})
const iter = rl[Symbol.asyncIterator]()
const readline = async () => (await iter.next()).value

function sumDigits2(n) {
    let sum = 0;
    while (n > 0) {
        sum += n % 10;
        n = Math.floor(n / 10);
    }
    return sum;
}

void async function () {
    const num = parseInt(await readline())
    if (num >= 1000 && num <= 9999) {

        console.log(sumDigits2(num))

    }else{
        console.log('输入数据不符合范围')
    }
    rl.close()
}()