XML - eXtensible Markup Language

XML gives a way of defining other markup languages (for example, HTML is a markup language that has an XML format). The "X" is for extensible, so XML is flexible in the data and documents that it can contain.

There is essentially no computer in the world, desk-top, hand-held, or back-room, that doesn't process XML sometimes. This is a good thing, because it shows that information can be packaged and transmitted and used in a way that's independent of the kinds of computer and software that are involved. XML won't be the last neutral information-wrapping system; but as the first, it's done very well.

Tim Bray (Sun Microsystems)

Quote from the press release of the W3C XML 10 Celebration in 2008

An example of course data in XML format is:

When working with XML in JavaScript, you can use the DOM, or there are libraries to convert XML to JSON.

One important aspect of XML is that it is really a family of technologies that interoperate quite well -- once you are in the XML world and using XML technologies, working with XML can be easy, straightforward, and even fun.  Examples of XML technolgoies are:

• Programming models:  DOM and SAX
• Query:  XQuery and XPath
• Transformation: XSLT
• Presentation format:  Office document formats are XML based, SVG (graphics), XSL-FO (print), XHTML/HTML (web)

So an example where we have the seasons array in XML:

<seasons>
  <season>Spring</season>
  <season>Summer</season>
  <season>Autumn</season>
  <season>Winter</season>
</seasons>

We could process that in jQuery by:

$.get("seasons.xml",function(data){
  var ul_node = $('<ul/>');
  console.log(data);
  $(data).find("season").each(function(){
    var season_string = $(this).text();
    console.log($(this));
    $('<li/>').text(season_string).appendTo(ul_node);
  });
  ul_node.replaceAll($('#seasonslist'));
});

Full code:

Working Examples:

• Live Example - Seasons in XML
• Seasons XML in JS Fiddle

Which is better, JSON or XML ? There are quite a few strong opinions as to whether JSON is better than XML or XML is better than JSON. The answer, of course, is "it depends". For delivering data to a web browser to process with JavaScript and present on a web page, JSON comes out ahead of XML. However, there are many cases where XML will be judged the winner over JSON.