The XMLHttpRequest Object
With the XMLHttpRequest object you can update parts of a web page, without reloading the whole page.
The XMLHttpRequest Object
The XMLHttpRequest object is used to exchange data with a server behind the scenes.
The XMLHttpRequest object is the developers dream, because you can:
- Update a web page without reloading the page
- Request data from a server after the page has loaded
- Receive data from a server after the page has loaded
- Send data to a server in the background
XMLHttpRequest Object Methods
| Method | Description |
|---|---|
| abort() | Cancels the current request |
| getAllResponseHeaders() | Returns header information |
| getResponseHeader() | Returns specific header information |
| open(method,url,async,uname,pswd) | Specifies the type of request, the URL, if the request should be handled asynchronously or not, and other optional attributes of a request
method: the type of request: GET or POST url: the location of the file on the server async: true (asynchronous) or false (synchronous) |
| send(string) | send(string) Sends the request off to the server. string: Only used for POST requests |
| setRequestHeader() | Adds a label/value pair to the header to be sent |
XMLHttpRequest Object Properties
| Property | Description |
|---|---|
| onreadystatechange | Stores a function (or the name of a function) to be called automatically each time the readyState property changes |
| readyState | Holds the status of the XMLHttpRequest. Changes from 0 to 4: 0: request not initialized 1: server connection established 2: request received 3: processing request 4: request finished and response is ready |
| responseText | Returns the response data as a string |
| responseXML | Returns the response data as XML data |
| status | Returns the status-number (e.g. "404" for "Not Found" or "200" for "OK") |
| statusText | Returns the status-text (e.g. "Not Found" or "OK") |
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