XMLHttpRequest Methods: getResponseHeader()
getResponseHeader() method of the
XMLHttpRequest object is used to get the string value of a named HTTP response header (or the value
null if the HTTP response headers have not been received yet or there was no specified header). CORS headers and
cookie headers are filtered out and cannot be queried. If the HTTP response has 2 or more headers with the specified name, then this method will return a space separated string of all the header values concatenated together.