make-it-modular.js

const dirReading = require('./directory-reading.js');
const dir = process.argv[2];
const filterExtension = process.argv[3];

const callback = (err, list) => {
    if (err) throw err;
    list.forEach(function (file) {
        console.log(file);
    })
}
dirReading(dir, filterExtension, callback);