From http://www.w3schools.com (Copyright Refsnes Data)

Why E4X?

E4X makes XML very simple to use.

E4X is Much Simpler

If you have ever tried to use JavaScript to parse and manipulate XML, you will find that E4X is much simpler to use.

Without E4X you have to use an XML library (or an XML component) to work with XML.

These libraries or components have different syntax and work differently in different browsers.

Without E4X

The following example is a cross browser example that loads an existing XML document ("note.xml") into the XML parser and displays the message from the note:

var xmlDoc
//code for Internet Explorer
if (window.ActiveXObject)
{
xmlDoc = new ActiveXObject("Microsoft.XMLDOM")
xmlDoc.async=false;
xmlDoc.load("note.xml")
displaymessage()
}
// code for Mozilla, Firefox, etc.
else (document.implementation && document.implementation.createDocument)
{
xmlDoc= document.implementation.createDocument("","",null)
xmlDoc.load("note.xml");
xmlDoc.onload=displaymessage
}

function displaymessage()
{
document.write(xmlDoc.getElementsByTagName("body")[0].firstChild.nodeValue)
}

Try it yourself

With E4X

The following example is the same as above but using E4X:

var xmlDoc=new XML()
xmlDoc.load("note.xml")
document.write(xmlDoc.body)

Much simpler, isn't it?