I’m using XMLHttpRequest on an embedded device that provides a non-standard extension to the

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Asked: May 25, 20262026-05-25T10:53:03+00:00 2026-05-25T10:53:03+00:00

I’m using XMLHttpRequest on an embedded device that provides a non-standard extension to the

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I’m using XMLHttpRequest on an embedded device that provides a non-standard extension to the API to allow manual cleanup of resources after the request has finished.

Can I assume that, for all cases (successful or otherwise, eg 404, DNS lookup failed, etc), a call to the send() method will eventually result in my onreadstatechange handler being called with readyState == 4?

Or, to put it another way, assuming that this implementation’s XHR behaves similarly to that of the standard browsers in all other ways, will the following code always result in the destroy() method being called?

var xhr = new XMLHttpRequest();
xhr.onreadystatechange = function () {
    if (xhr.readyState == 4) {
        callback(xhr.responseText);
        if (xhr.destroy) { // must call this to prevent memory leak
            xhr.destroy();
        }
    }       
};
xhr.open(method, url, true);
xhr.send(null);