NodeJS使用递归算法和遍历算法来遍历目录的方法

function factorial(n) {
    if (n === 1) {
        return 1;
    } else {
        return n * factorial(n - 1);
    }
}

          A
         / \
        B   C
       / \   \
      D   E   F

function travel(dir, callback) {
    fs.readdirSync(dir).forEach(function (file) {
        var pathname = path.join(dir, file);

        if (fs.statSync(pathname).isDirectory()) {
            travel(pathname, callback);
        } else {
            callback(pathname);
        }
    });
}

- /home/user/
    - foo/
        x.js
    - bar/
        y.js
    z.css

travel('/home/user', function (pathname) {
    console.log(pathname);
});

------------------------
/home/user/foo/x.js
/home/user/bar/y.js
/home/user/z.css

function travel(dir, callback, finish) {
    fs.readdir(dir, function (err, files) {
        (function next(i) {
            if (i < files.length) {
                var pathname = path.join(dir, files[i]);

                fs.stat(pathname, function (err, stats) {
                    if (stats.isDirectory()) {
                        travel(pathname, callback, function () {
                            next(i + 1);
                        });
                    } else {
                        callback(pathname, function () {
                            next(i + 1);
                        });
                    }
                });
            } else {
                finish && finish();
            }
        }(0));
    });
}