Five Steps for AJAX applications

1. Establish XMLHttpRequest objects

if (window. XMLHttpRequest) {
XmlHttp = new XMLHttpRequest ();

if (Xmlhttp.overridemimetype) {
Xmlhttp.overridemimetype ("Text/xml");
}
}else if (window. ActiveXObject) {
var activename =["MSXML2. XMLHTTP "," Microsoft.XMLHTTP "];
for (var i=0; i<activename.length; i++) {
try{
XmlHttp = new ActiveXObject (Activename[i]);
Break
}catch (e) {
}
}

}
if (!xmlhttp) {
Alert ("Create XMLHttpRequest object Failed");
}else{

}

2. Set callback function

Xmlhttp.onreadystatechange= callback;

function callback () {}

3. Use the Open method to establish a connection with the server Xmlhttp.open ("Get", "ajax?name=" + name,true)

This step is to set the request for HTTP (post/get), and if it is post, pay attention to setting the request header information Xmlhttp.setrequestheader ("Content-type", "application/ X-www-form-urlencoded ")

4. Send data to server side

Xmlhttp.send (NULL);

If the Post method is not empty

5. Handling in a callback function for different response states

if (xmlhttp.readystate = = 4) {
Determine if the interaction is successful
if (Xmlhttp.status = = 200) {
Get data returned by the server
Get Plain Text data
var responsetext =xmlhttp.responsetext;
document.getElementById ("Info"). InnerHTML = ResponseText;
}
}