Success

response.ok property lets you distinguish good from bad HTTP response statuses

• property is set to true only if the response has status (200-299)

Errors

Client errors (400–499) Server errors (500–599)

Errors must be explicitly handled when making a fetch request

async function fetchResultsIn404() {
  const response = await fetch('/error');
  
  response.ok;     // => false
  response.status; // => 404

  const text = await response.text();
  return text; // 'Page not found'
}

When above code is executed, the resource request results in an error

• Without explicit error handling, the function returns a string instead of an Error which is considered a completed HTTP request

Throwing Error

async function fetchBadStatus() {
  const response = await fetch('/oops');

  if (!response.ok) {
    const message = `An error has occured: ${response.status}`;
    throw new Error(message);
  }

  const movies = await response.json();
  return movies;
}

fetchBadStatus().catch(error => {
  error.message; // 'An error has occurred: 404'
});