XMLHttpRequest:
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:
- PropertyDescription
- 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.
- 4DONE 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:
- MethodDescription
- 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.