The XMLHttpRequest Object
With the XMLHttpRequest object you can update parts of a web page, without reloading the whole page.
Try it Yourself - Examples
A
simple XMLHttpRequest example
Create a simple XMLHttpRequest, and retrieve data from a TXT file.
Retrieve header information with getAllResponseHeaders()
Retrieve header information of a resource (file).
Retrieve specific header information with getResponseHeader()
Retrieve specific header information of a resource (file).
Retrieve the content of an ASP file
How a web page can communicate with a web server while a user type characters in an input field.
Retrieve content from a database
How a web page can fetch information from a database with the XMLHttpRequest object.
Retrieve the content of an XML file
Create an XMLHttpRequest to retrieve data from an XML file and display the data in an HTML table.
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") |
