Learn to use ECMAScript (aka JavaScript) for XML (E4X), and discover of technical articles and tips, tutorials, standards, and IBM Redbooks. ECMAscript for XML (more colloquially known as E4X) has had comparatively limited success of adoption in the face of the power of JSON. E4X: ECMAScript for XML ECMAScript for XML, better known as E4X, is a standard extension[22] to JavaScript This section presents a quick tutorial on E4X.

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If you have several branches within your XML and want to get all users over lbs, you can use the descendants property. The text value of an element with a primitive value no element children or of an attribute can be obtained explicitly as a string by the toString method, but in most circumstances the toString method will be called automatically when tutkrial string value is needed.

E4X Quick Start Guide

The JavaScript scripting language is extremely simple and well organized. To change the value of an element or attribute, titorial a new value to it, as in Listing At the end of this method you have the expression linkNode.

This information is extracted from the ECMA specification [1]. This exercise is also making the implicit assumption that the syndication feed is in Atom format, though the same basic rules apply for most XML-compliant RSS 2. Iterations and Filters This use of iterating through an object represent another area where E4X equalizes the field.

E4X is zero-based, so the index value used to retrieve the third record is 2. E4X has a similar construct:. A list of all processing instructions that are children of this element. Admittedly, in this case it doesn’t make that much difference determining the feed is relatively simplebut from a security standpoint f4x provides a layer of protection on potentially sensitive information.

Introducing E4X

For other kinds of objects, the value of the object. Perhaps one of the biggest benefit of using E4X stems from the fact that most database systems and consequently many web sites are now moving towards producing XML content natively, whereas relatively few are doing the same thing with JSON feeds which consequently need to be crafted by hand.


Now, it’s time to formally introduce you. The following access examples are based on the xmlMusic object created above.

JavaScript: The Definitive Guide, 6th Edition by David Flanagan

Notice that one writes “c. Returns the child element with the given propertyName, or if propertyName is an integer, returns the child in that position. Thus, it is necessary to run a quick regular expression to remove all of these:.

Sets the name of the XML object to the requested value possibly qualified. E4X recognizes two fundamental types: Namespaces in E4X are something of a tutroial, for much the same reason that they are a headache in XML in general.

Adds child as a new child of the element, after all other children.

E4X: JavaScript on steroids

Dot and hyphen already have tuorial within Javascript, so when referring to an XML element containing one of those characters, an escaping mechanism must be employed. If you get this far then it is likely a configuration issue within your development module. This hutorial start guide should not only give you the basics of E4X, but also point out some of the tricky cases that an intermediate user will likely encounter.

Employing the insertBefore method, the song “Eleven Four,” is placed between the current song nodes.

For instance, suppose that you wanted to look through a set of phone numbers to find the ones that are in the “” local exchange the first three numbers tuotrial the seven digit version of the telephone number. You can download the example attached below and f4x along. One interesting consequence of this is that because the selectFeed function is then assigned at that point to the selection box listing the titles, the feed itself remains in memory, but is completely inaccessible to anything beyond the selectFeed function.

However, not all browsers support it. The constructor can take either a string or an E4X object as an tutoriak the first will be parsed as XML if it’s well formedthe second will be passed through unchanged. Instead of returning the XML representation, it returns the concatenated text of all of the text nodes in the E4X object.


One useful construct in XPath is the predicate notation e. You can get the actual count with the length function: Returns true for attributes, text nodes, or elements without child elements, otherwise false.

You can get tutroial actual count with the length function:.

You can access the attributes of the XML object using the at sign tutoral. Only if no such name is found are variables checked. For elements with element children, returns same as toXMLString. For example, to list all the attributes of the xmlMusic object, use the code in Listing The power, flexibility, and simplicity of E4X is forcefully demonstrated here. With the aid of the length method, all the nodes that have the jazz attribute are output by the code in Listing Returns the namespace associated with this object, or if a prefix is specified, an in-scope namespace with that prefix.

What about parsing and serializing? Event ; import flash.

It’s also possible to remove an item from an existing E4X object via the delete command. First things first, are you using NetKernel version 2.

For instance, suppose that you had an object version of the phone book and you wanted to create a table showing the names and numbers of each person in the book. Returns the descendant elements children, grandchildren, etc.

NET in general require that you roll your own parsers and serializers. A child attribute can be accessed by name using the ” ” prefix, or with the attribute method. To demonstrate the power and flexibility of E4X, I describe the main tutorkal employed to manipulate XML data, using a music catalog as the main input source. Bach now has two compositions as part of the xmlMusic object, where prior to this statement there was only one. All the listed methods are available to XML objects.