callback_and_promises.js

const func1 = (a, b, callback) => {
  callback(a + b);
};

const func2 = (a, b) => {
  func1(a, b, result => {
    console.log(result);
  });
};

func2(19, 10);

func3 = (a, b) => {
  return new Promise((resolve, reject) => {
    try {
      if (b <= 0) throw "assim nao dá";
      const c = a / b;
      resolve(c);
    } catch (e) {
      reject(e);
    }
  });
};

func3(19, 0)
  .then(console.log)
  .catch(console.log)
  .finally(console.log);