The XMLHttpRequest.responseXML read-only property returns a Document containing the HTML or XML retrieved by the request; or null if the request was unsuccessful, has not yet been sent, or if the data can't be parsed as XML or HTML. 
 Note: The name responseXML is an artifact of this property's history; it works for both HTML and XML. 
 Usually, the response is parsed as "text/xml". If the responseType is set to "document" and the request was made asynchronously, instead the response is parsed as "text/html". responseXML is null for any other types of data, as well as for data: URLs. 
 If the server doesn't specify the Content-Type as "text/xml" or "application/xml", you can use XMLHttpRequest.overrideMimeType() to parse it as XML anyway. 
This property isn't available to workers.