file1.js

const file2 = require('./file2');

console.log(`Greet -> ${file2.getGreet('Bares')}`);
console.log(`Sum -> ${file2.sum('1', '5')}`);

file2.js

exports.getGreet = (name) => `Salve signor ${name}, si ricorda di me?`;
exports.sum = (str1, str2) => (str1 | 0) + (str2 | 0);

package.json

{
  "name": "base",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "start": "node file1.js"
  },
  "keywords": [],
  "author": "Alberto Schiabel (https://github.com/jkomyno)",
  "license": "MIT"
}

npm start