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The for each..in Loop

As you can see, E4X represents a radical departure from traditional ECMAScript to support XML in a

simple yet powerful manner.

Throughout the book, you have used the

for..in

loop to iterate over property names of an object. The

for each..in

loop, introduced in E4X, iterates the actual objects in an array. For example:

for each (var oItem in arrItems) {

alert(oItem);

}

To accomplish the same thing using a

for..in

loop, you use code that looks like this:

for (var sProperty in arrItems) {

alert(arrItems[sProperty]);

}

As you can see, the

for each..in

loop is a lot more useful and more like similar loops in other languages.

New classes

E4X introduces several new classes to deal specifically with XML:

Namespace

objects represent namespaces by using a URI and a prefix.

QName

objects represent XML qualified names composed of a local name and an optional

namespace URI.

XML

objects represent individual XML elements.

XMLList

objects contain any number of XML objects.

The Namespace class

Namespace

objects are a convenient way to reference namespaces in E4X. To create a

Namespace

, use its

constructor with one or two arguments:

var oNamespace1 = new Namespace(“http://www.wrox.com/”);

var oNamespace2 = new Namespace(“wrox”, “http://www.wrox.com/”);

In the first line, the constructor is called with just the URI of the namespace, which can be used when

dealing with XML like this:

<message>Hello World!</message>

</root>

In the second line of the example, the constructor is being called with a namespace prefix and the URI,

which is useful when dealing with XML code that looks like this:

<wrox:root xmlns:wrox=”http://www.wrox.com/”>

<wrox:message>Hello World!</wrox:message>

</wrox:root>

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