ajax.readyState
0 - (uninitialized) has not been called send () method
1-- (load) has been called send () method, is sending request
2 - (Loaded) Send () method performs is completed, the entire response has been received
3 - (interactive) response is being parsed
4 - (complete) response content analysis is complete, you can call the client
HTTP status code ajax.status
1 **: Request received, continuing process
2 **: operating successfully received, analyzed, accepted
** 3: complete the request must be further processed
4 **: a request contains bad syntax or can not be completed
5 **: a server performs perfectly valid request failed
100-- customers must continue to make requests
101-- client asks the server to convert the HTTP protocol version upon request
200-- trading success
201-- prompted know the new URL file
202-- accept and deal with, but the process is not completed
203-- return uncertain or incomplete information
204-- requests received, but returned information is null
205-- server completes the request, the user agent must reset the current document has been visited
206-- server has completed GET request some users
300-- resource request may be obtained in many
301-- deletion request data
302-- address found in other requested data
303-- advise clients to access the URL or other access methods
304-- client has performed a GET, but the file does not change
305-- resources must be requested from the server specified address
306-- HTTP previous version of code used in the current version is no longer in use
307-- stated delete temporary resource request
400-- Bad Request, such as syntax errors
401-- request authorization failed
402-- effective retention head in response ChargeTo
403-- request is not allowed
404-- not find the file, query or URl
405-- method does not allow the user fields defined in Request-Line
406-- according to Accept sent by the user to drag, the requested resource is not accessible
407-- similar 401, the user must first be authorized on the proxy server
408-- client request is not completed within a user-specified time hungry
409-- on the current status of the resource, the request can not be completed
410-- no longer have this resource on the server and no further reference address
411-- server denies the user-defined attribute request Content-Length
412-- request one or more header fields in the current request error
413-- resource request is larger than the size allowed by the server
414-- resources requested URL is longer than the length allowed by the server
415-- requested resource request is not supported project format
416-- request request including a Range header field is not within the range value indicating the current request resources, the request does not comprise Request If-Range header field
417-- server does not meet a desired value specified by the request Expect header field, if a proxy server may be a server can not satisfy the request
500-- generate an internal server error
501-- server does not support the requested function
502-- server is temporarily unavailable, and sometimes to prevent system overload
503-- server overload or suspend service
504-- overload mark, use another gateway server in response to a user or service, set a longer waiting time value
505-- server does not support or refuses to support the specified HTTP request header version