Two different approaches to List files in NodeJS

list.js

let start = new Date();
require('fs').readdir(require('path').join(__dirname), (err, files) => {
    if (! err) {
        files.forEach(function (file) {
            require('./' + file);
        });
    }
});
console.log(new Date() - start + 'ms'); //  1 ' ms'


start = new Date();
require('util').promisify(require('child_process').exec)('dir').then((out, err) => {

});
console.log(new Date() - start + 'ms'); // 12 ' ms'