failure-first-approach.js

failure-first-approach.js

// do we have errors?
if (condition === false) {
  return new Error('reason goes here') ||  Promise.reject(new Error('reason goes here')); // either
}

// are tasks needed?
if (condition === false) {
  return tasks();
}
return Promise.resolve();

xhr(...parameters)
  .then((result) => {
    const { error } = result;
    if (error !== undefined) {
      console.log(error); // application error
    }
    console.log(result); // ok
  })
  .catch((error) => {
    console.log(error); // network error, 4xx / 5xx
  });