AJAX & Async Requests·AJAX from first request to live updates

Error handling

Separate network, HTTP, parse and application errors.

Beginner 13 min read Lesson 6 of 300 Challenge included

What you will be able to do

Use try/catch for network errors.
Check response.status for HTTP errors.
Wrap JSON parsing separately.
Show an actionable message.

In plain English

Different failures need different messages. A network error means connectivity; a 401 means sign in; a 422 means fix the form; a 500 means retry later. Do not show a generic "something went wrong" for all of them.

errors.jsJavaScript

try {
  const response = await fetch('/api/save', { method: 'POST', body })
  if (response.status === 401) return showSignIn()
  if (response.status === 422) return showFieldErrors(await response.json())
  if (!response.ok) throw new Error('Retry later')
} catch {
  showOfflineMessage()
}

Your turn

Handle a 422

Medium

Show field errors when the response status is 422.

JAVASCRIPT · starter

if (!response.ok)

Check your understanding before moving on.

Knowledge checkQuestion 1

Which status code usually means the user must sign in?

Select an answer to continue

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