RE: What are the different readystates in XMLHttpRequest?
The XMLHttpRequest.readyState property returns the state an XMLHttpRequest client is in
Value State Description
0 UNSENT Client has been created. open() not called yet.
1 OPENED open() has been called.
2 HEADERS_RECEIVED send() has been called, headers & status are available.
3 LOADING Downloading; responseText holds partial data.
4 DONE The operation is complete.