Native JS encapsulated Ajax (principle)

1. Create an Ajax object
var oajax=new xmlhttprequest ();
2. Connect
oajax.open (' GET ', ' a.txt ' + '? ') +data,true);
oajax.open (' POST ', url,true);
3. Send
oajax.send ();
oajax.setrequestheader (' Content-type ', ' application/x-www-form-urlencoded ');
oajax.send (data);
4. Receiving
Monitor
Oajax.onreadysatechange
oajax.readystate
0-(uninitialized) has not yet called the Send () method
1-(load) called the Send () method, sending the request
2-(loading complete) the Send () method executes and has received the full response content
3-(interactive) parsing response content
4-(complete) The response content resolution is complete and can be invoked on the client
Oajax.status
200 Successes
200-299 is a success .
304 Not modified

Native JS encapsulated Ajax (principle)