Understanding XMLHttpRequestAn 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 objectThe common properties of XMLHttpRequest object are as follows: Property | Description |
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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 objectThe important methods of XMLHttpRequest object are as follows: Method | Description |
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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. |
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