If you need to handle error messages using jQuery.AJAX you will need to modify the xhr function so the responseType is not being modified when an error happens.
So you will have to modify the responseType to "blob" only if it is a successful call:
$.ajax({
...
xhr: function() {
var xhr = new XMLHttpRequest();
xhr.onreadystatechange = function() {
if (xhr.readyState == 2) {
if (xhr.status == 200) {
xhr.responseType = "blob";
} else {
xhr.responseType = "text";
}
}
};
return xhr;
},
...
error: function(xhr, textStatus, errorThrown) {
// Here you are able now to access to the property "responseText"
// as you have the type set to "text" instead of "blob".
console.error(xhr.responseText);
},
success: function(data) {
console.log(data); // Here is "blob" type
}
});
If you debug and place a breakpoint at the point right after setting the xhr.responseType to "blob" you can note that if you try to get the value for responseText you will get the following message:
The value is only accessible if the object's 'responseType' is '' or 'text' (was 'blob').