题解 | 反向输出一个四位数

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

void (async function () {
    const lines = await readline();
    const arr = [];
    if (parseInt(lines) >= 1000 && parseInt(lines) <= 9999) {
        for (let i = 0; i < lines.length; i++) {
            arr.unshift(lines[i]);
        }
        console.log(arr.join(""));
    } else {
        console.log("输入了非法字符或不是范围内的数字");
    }

    rl.close();
})();