How to Detect Cross Origin (CORS) Error vs. Other Types of Errors for XMLHttpRequest() in Javascript

Question

I\'m trying to detect when an XMLHttpRequest() fails due to a Cross Origin Error as opposed to a bad request. For example:

    ajaxObj=new XMLHttpRequest()
         


        

Answer 1

Maybe in case it helps anyone... one other way to handle difference between cors and network error... can work with chrome or firefox... (not perfect solution though)

var external = 'your url';

if (window.fetch) {
    // must be chrome or firefox which have native fetch
    fetch(external, {'mode':'no-cors'})
        .then(function () {
            // external is reachable; but failed due to cors
            // fetch will pass though if it's a cors error
        })
        .catch(function () {
            // external is _not_ reachable
        });
} else {
    // must be non-updated safari or older IE...
    // I don't know how to find error type in this case
}