📅  最后修改于: 2022-03-11 15:02:00.880000             🧑  作者: Mango
//Ajax 5 states of requests
0 UNSENT open() has not been called yet.
1 OPENED send() has been called.
2 HEADERS_RECEIVED send() has been called, and headers and status are available.
3 LOADING Downloading; responseText holds partial data.
4 DONE The operation is complete.