无法从目录中递归提取所有文本文件名

我想把所有的 txt 以递归方式(即搜索所有子文件夹)来自目录的文件:

let fs = require("fs");

function getPathNames(dirName) {
    let pathNames = [];
    for (let fileName of fs.readdirSync(dirName)) {
        let pathName = dirName + "/" + fileName;
        if (fs.statSync(pathName).isDirectory())
            pathNames.concat(getPathNames(pathName));
        else if (pathName.endsWith(".txt"))
            pathNames.push(pathName);
    }
    return pathNames;
}

但是,当我打电话的时候 getPathNames(".") ,我只得到第一个文件的名称。

如果我将返回值从函数中取出,并改为更新全局变量,它会很好地工作:

let fs = require("fs");

let pathNames = [];

function getPathNames(dirName) {
    for (let fileName of fs.readdirSync(dirName)) {
        let pathName = dirName + "/" + fileName;
        if (fs.statSync(pathName).isDirectory())
            getPathNames(pathName);
        else if (pathName.endsWith(".txt"))
            pathNames.push(pathName);
    }
}

有人发现第一种方法有什么问题吗?

谢谢您!