An object of XMLHttpRequest is used for asynchronous communication between client and server.
It performs following operations:
- Sends data from the client in the background
- Receives the data from the server
- Updates the webpage without reloading it.
Properties of XMLHttpRequest object
The common properties of XMLHttpRequest object are as follows:
|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|
Methods of XMLHttpRequest object
The important methods of XMLHttpRequest object are as follows:
|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.|