XML DOM - HttpRequest 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")