I've encountered a unexpected behavior in my fetch code when the internet connection is slow. Consider the following code (not my actual code):

function handleErrors(response) {
    if (!response.ok) {
        throw Error(response.statusText);
    }
    return response;
}
fetch("http://url")
    .then(handleErrors)
    .then(response => console.log("success") )
    .catch(error => console.log("error") );

// "error"
// "success" (why is this called?)

The only way I can explain this behaviour is that the response is somewhat of an async function itself (check out https://stackoverflow.com/a/33446005/3016745). Meaning that first the request is sent, immediately after the connection times out and throws an error, and last the response is coming and calls the .then.

I checked the backend and the request and response both were successful.

Does this make sense? How do I prevent this behaviour?