XMLHttpRequest Properties

• onreadystatechange
  An event handler for an event that fires at every state change.
• readyState
  The readyState property defines the current state of the XMLHttpRequest object.
  Here are the possible values for the readyState propery:

  State	Description
  0	The request is not initialized
  1	The request has been set up
  2	The request has been sent
  3	The request is in process
  4	The request is completed

  readyState=0 after you have created the XMLHttpRequest object, but before you have called the open() method.
  readyState=1 after you have called the open() method, but before you have called send().
  readyState=2 after you have called send().
  readyState=3 after the browser has established a communication with the server, but before the server has completed the response.
  readyState=4 after the request has been completed, and the response data have been completely received from the server.
• responseText
  Returns the response as a string.
• responseXML
  Returns the response as XML. This property returns an XML document object, which can be examined and parsed using W3C DOM node tree methods and properties.
• status
  Returns the status as a number (e.g. 404 for "Not Found" and 200 for "OK").
• statusText
  Returns the status as a string (e.g. "Not Found" or "OK").