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XML Tutorial

XML HOMEXML IntroductionXML How to useXML TreeXML SyntaxXML ElementsXML AttributesXML NamespacesXML DisplayXML HttpRequestXML ParserXML DOMXML XPathXML XSLTXML XQueryXML XLinkXML ValidatorXML DTDXML SchemaXML ServerXML ExamplesXML QuizXML Certificate

XML AJAX

AJAX IntroductionAJAX XMLHttpAJAX RequestAJAX ResponseAJAX XML FileAJAX PHPAJAX ASPAJAX DatabaseAJAX ApplicationsAJAX Examples

XML DOM

DOM IntroductionDOM NodesDOM AccessingDOM Node InfoDOM Node ListDOM TraversingDOM NavigatingDOM Get ValuesDOM Change NodesDOM Remove NodesDOM Replace NodesDOM Create NodesDOM Add NodesDOM Clone NodesDOM Examples

XPath Tutorial

XPath IntroductionXPath NodesXPath SyntaxXPath AxesXPath OperatorsXPath Examples

XSLT Tutorial

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XQuery Tutorial

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XML DTD

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XSD Schema

XSD IntroductionXSD How ToXSD <schema>XSD ElementsXSD AttributesXSD RestrictionsXSD Complex ElementsXSD EmptyXSD Elements-onlyXSD Text-onlyXSD MixedXSD IndicatorsXSD <any>XSD <anyAttribute>XSD SubstitutionXSD Example

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References

DOM Node TypesDOM NodeDOM NodeListDOM NamedNodeMapDOM DocumentDOM ElementDOM AttributeDOM TextDOM CDATADOM CommentDOM XMLHttpRequestDOM ParserXSLT ElementsXSLT/XPath Functions

AJAX Introduction

AJAX is a developer's 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

Try it Yourself Examples in Every Chapter

In every chapter, you can edit the examples online, and click on a button to view the result.

AJAX Example

Let AJAX change this text

Try it Yourself »


AJAX Example Explained

HTML Page

<!DOCTYPE html>
<html>
<body>

<div id="demo">
  <h2>Let AJAX change this text</h2>
  <button type="button" onclick="loadDoc()">Change Content</button>
</div>

</body>
</html>

The HTML page contains a <div> section and a <button>.

The <div> section is used to display information from a server.

The <button> calls a function (if it is clicked).

The function requests data from a web server and displays it:

Function loadDoc()

function loadDoc() {
  var xhttp = new XMLHttpRequest();
  xhttp.onreadystatechange = function() {
    if (this.readyState == 4 && this.status == 200) {
     document.getElementById("demo").innerHTML = this.responseText;
    }
  };
  xhttp.open("GET", "ajax_info.txt", true);
  xhttp.send();
}

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>


What is AJAX?

AJAX = Asynchronous JavaScript And XML.

AJAX is not a programming language.

AJAX just uses a combination of:

  • A browser built-in XMLHttpRequest object (to request data from a web server)
  • JavaScript and HTML DOM (to display or use the data)

AJAX is a misleading name. AJAX applications might use XML to transport data, but it is equally common to transport data as plain text or JSON text.

AJAX allows web pages to be updated asynchronously by exchanging data with a web server behind the scenes. This means that it is possible to update parts of a web page, without reloading the whole page.


How AJAX Works

  • 1. An event occurs in a web page (the page is loaded, a button is clicked)
  • 2. An XMLHttpRequest object is created by JavaScript
  • 3. The XMLHttpRequest object sends a request to a web server
  • 4. The server processes the request
  • 5. The server sends a response back to the web page
  • 6. The response is read by JavaScript
  • 7. Proper action (like page update) is performed by JavaScript