In web programming (JavaScript, Dart, etc), how can I tell if my XMLHttpRequest (aka AJAX) request failed because of a network error?

I define network error as anything like DNS, TCP, connection issues, etc.

Thanks!

In web programming (JavaScript, Dart, etc), how can I tell if my XMLHttpRequest (aka AJAX) request failed because of a network error?

I define network error as anything like DNS, TCP, connection issues, etc.

Thanks!

• javascript
• web
• dart

• Have a Look - stackoverflow./questions/1730692/… – Ankit Commented Jan 20, 2014 at 18:45
• The timeout doesn't always work. I tested locally with my server turned off, and the XHR request failed instantly. In some cases, timeout probably works as one indicator. – Seth Ladd Commented Jan 20, 2014 at 19:03

3 Answers 3

In Dartium, and in Chrome JS at least, you can detect the failure by seeing that you hit readyState == 4 ("done") with a status of zero. Zero is not a valid server response, all HTTP server responses are above 100, so it means that it didn't actually reach the server (or at least the server didn't speak proper HTTP).

The onError stream will also get a progress event at this point.

In synchronous mode, the error will be thrown instead.

Usually the answer of the AJAX calls e with a status code, and a responseText properties, if you have access to the data that es from the call, try to read data.status and data.responseText and see if you get them correctly (200 is for success, 500 is for internal server error, etc).

u need to check, what response code is returned from in response, if that code is returning 500, means there is a server issue.