An object of XMLHttpRequest is used for asynchronous communication between client and server.
It performs following operations:
The common properties of XMLHttpRequest object are as follows:
| Property | Description |
|---|---|
| onReadyStateChange | It is called whenever readystate attribute changes. It must not be used with synchronous requests. |
| readyState | represents the state of the request. It ranges from 0 to 4.
0 UNOPENED open() is not called. 1 OPENED open is called but send() is not called. 2 HEADERS_RECEIVED send() is called, and headers and status are available. 3 LOADING Downloading data; responseText holds the data. 4 DONE The operation is completed fully. |
| reponseText | returns response as text. |
| responseXML | returns response as XML |
The important methods of XMLHttpRequest object are as follows:
| Method | Description |
|---|---|
| void open(method, URL) | opens the request specifying get or post method and url. |
| void open(method, URL, async) | same as above but specifies asynchronous or not. |
| void open(method, URL, async, username, password) | same as above but specifies username and password. |
| void send() | sends get request. |
| void send(string) | send post request. |
| setRequestHeader(header,value) | it adds request headers. |
