AJAX - Server Response

The onreadystatechange Property

The readyState property holds the status of the XMLHttpRequest.

The onreadystatechange property defines a function to be executed when the readyState changes.

The status property and the statusText property holds the status of the XMLHttpRequest object.

Property	Description
onreadystatechange	Defines a function to be called when the readyState property changes
readyState	Holds the status of the XMLHttpRequest. 0: request not initialized 1: server connection established 2: request received 3: processing request 4: request finished and response is ready
status	200: "OK" 403: "Forbidden" 404: "Page not found" For a complete list go to the Http Messages Reference
statusText	Returns the status-text (e.g. "OK" or "Not Found")

The onreadystatechange function is called every time the readyState changes.

When readyState is 4 and status is 200, the response is ready:

Example

Try it Yourself »

The "ajax_info.txt" file used in the example above, is a simple text file and looks like this:

<h1>AJAX</h1>
<p>AJAX is not a programming language.</p>
<p>AJAX is a technique for accessing web servers from a web page.</p>
<p>AJAX stands for Asynchronous JavaScript And XML.</p>

The onreadystatechange event is triggered four times (1-4), one time for each change in the readyState.

Using a Callback Function

A callback function is a function passed as a parameter to another function.

If you have more than one AJAX task in a website, you should create one function for executing the XMLHttpRequest object, and one callback function for each AJAX task.

The function call should contain the URL and what function to call when the response is ready.

Example

loadDoc(" url-1", myFunction1);

loadDoc(" url-2", myFunction2);

function loadDoc(url, cFunction) {
var xhttp;
xhttp=new XMLHttpRequest();
xhttp.onreadystatechange = function() {
    if (this.readyState == 4 && this.status == 200) {
      cFunction(this);
    }
};
  xhttp.open("GET", url, true);
  xhttp.send();
}

function myFunction1(xhttp) {
// action goes here
}
function myFunction2(xhttp) {
// action goes here
}

Try it Yourself »

Server Response Properties

Property	Description
responseText	get the response data as a string
responseXML	get the response data as XML data

Server Response Methods

Method	Description
getResponseHeader()	Returns specific header information from the server resource
getAllResponseHeaders()	Returns all the header information from the server resource

The responseText Property

The responseText property returns the server response as a JavaScript string, and you can use it accordingly:

Example

document.getElementById("demo").innerHTML = xhttp.responseText;

Try it Yourself »

The responseXML Property

The XML HttpRequest object has an in-built XML parser.

The responseXML property returns the server response as an XML DOM object.

Using this property you can parse the response as an XML DOM object:

Example

Request the file cd_catalog.xml and parse the response:

xmlDoc = xhttp.responseXML;
txt = "";
x = xmlDoc.getElementsByTagName("ARTIST");
for (i = 0; i < x.length; i++) {
txt += x[i].childNodes[0].nodeValue + "<br>";
}
document.getElementById("demo").innerHTML = txt;
xhttp.open("GET", "cd_catalog.xml", true);
xhttp.send();

Try it Yourself »

You will learn a lot more about XML DOM in the DOM chapters of this tutorial.

The getAllResponseHeaders() Method

The getAllResponseHeaders() method returns all header information from the server response.

Example

var xhttp = new XMLHttpRequest();
xhttp.onreadystatechange = function() {
if (this.readyState == 4 && this.status == 200) {
document.getElementById("demo").innerHTML =
this.getAllResponseHeaders();
}
};

Try it Yourself »

The getResponseHeader() Method

The getResponseHeader() method returns specific header information from the server response.

Example

Try it Yourself »

❮ Previous Next ❯