AJAX XMLHttpRequest Properties
Following are AJAX XMLHttpRequest properties.
onreadystatechange
Before you calling send method, Using onreadystatechange event to set callback (handler) function to be executed when the status of the request changes,
Syntax
xhr.onreadystatechange = function() {
......
};
readyState
readyState property returns the status of the request.
Different States
| Constant Name | State Value | Description |
|---|---|---|
| UNSENT | 0 | uninitialized open() method has not been called. |
| OPENED | 1 | unsend send() method has not yet been called. |
| HEADERS_RECEIVED | 2 | send send() method has been called and headers and status data are available. |
| LOADING | 3 | receiving Data receiving from server and responseText holds the receiving data. |
| DONE | 4 | completed Ajax request finished. |
Syntax
var current_state = xhr.readyState;
Example You can use either constant name or state value.
xhr.onreadystatechange = function() {
if (xhr.readyState == 4) {
alert(xhr.responseText);
}
};
xhr.onreadystatechange = function() {
if (xhr.readyState == xhr.DONE) {
alert(xhr.responseText);
}
};
Alternative way, If you concern about only state = 4 (DONE), use the onload event.
xhr.onload = function() {
...
};
status
When a request is received on server, Server return the HTTP status code using status property. for example, status code 200 for Ok, 408 for Request timeout, 404 for Request not found.
Syntax
var xhr_status = xhr.status;
Example
if (xhr.readyState == xhr.DONE){
if ((xhr.status == 200) || (xhr.status == 0)){
alert(xhr.status);
}
}
statusText
Same as above server return HTTP status string Request ok for 200, Request timeout for 408, Request not found for 404.
Syntax
var xhr_statustext = xhr.statusText;
Example
if (xhr.readyState == xhr.DONE){
if ((xhr.status == 200) || (xhr.status == 0)){
alert(xhr.statusText);
}
}
responseText/XML/Body
responseText Requested response return as a string data as a string object.
Example
var xhr_responseText = xhr.responseText;
responseXML Requested response return as a XML data as a XML object.
Example :
var xhr_responseXML = xhr.responseXML;
responseBody This property is use when XHR object created as a ActiveX component (for IE 5 & 6).
Example
var xhr_responseBody = xhr.responseBody;