Uninitialized: An XMLHttpRequest object has been created, but not initialized
Ready: Code has called the XMLHttpRequest open() method, and theXMLHttpRequest object is ready to send a request to the server
Sent: A request has been sent from the client to the server with thesend() method, but a response has not yet been received
Receiving: The HTTP response headers have been received from the server,but the message body has not yet been completely received fromthe client
Loaded: The response has been completely received by the client.