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;

void (async function () {
    const num = parseInt(await readline());
    if (num >= 1000 && num <= 9999) {
        const a = num % 10;
        const b = Math.floor((num / 10) % 10);
        const c = Math.floor((num / 100) % 10);
        const d = Math.floor((num / 1000) % 10);
        console.log(a + b + c + d);
    } else {
        console.log("输入数据不符合范围");
    }
    rl.close();
})();