E4X TUTORIAL PDF

Warning: E4X is obselete. It's been disabled by default for chrome in Firefox 17, and completely removed in Firefox First introduced in JavaScript 1. A full definition of E4X can be found in the Ecma specification. This chapter provides a practical overview of the language; it is not a complete reference.

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Warning: E4X is obselete. It's been disabled by default for chrome in Firefox 17, and completely removed in Firefox First introduced in JavaScript 1. A full definition of E4X can be found in the Ecma specification. This chapter provides a practical overview of the language; it is not a complete reference.

This practice is no longer necessary, but remains in some legacy code. E4X offers two principal ways of creating an XML object. The first is to pass a string to the XML constructor:. In both cases, the resulting object will be an E4X XML object, which provides convenient syntax for both accessing and updating the encapsulated data. While the XML object looks and behaves in a similar way to a regular JavaScript object, the two are not the same thing.

The syntax is designed to be familiar to JavaScript programmers, but E4X does not provide a direct mapping from XML to native JavaScript objects; just the illusion of one. It is possible to interpolate variables into an XML literal to create an element name or to create content.

XML literal syntax has a significant advantage over the XML constructor when you need to create markup dynamically. With E4X it is easy to embed dynamic values in markup. Upon execution the variable is evaluated and quotes are automatically added where appropriate. Less than and ampersand signs are escaped into their entity equivalents. It is not possible to directly interpolate variables amidst other literal or variable attribute content, however e.

One must instead either calculate the variable with a JavaScript expression e. This node has one attribute, type, which can be accessed and updated in a number of ways:. Note that if one wishes to make comparisons of retrieved attributes with other strings, it is necessary to convert the attribute first, even though the attribute may be converted to a string when used in other contexts such as insertion into a textbox. XML objects provide a number of methods for inspecting and updating their contents.

They support JavaScript's regular dot and [] notation, but instead of accessing object properties E4X overloads these operators to access the element's children:. If you access something with more than one matching element, you get back an XMLList :. While the. The length method here returns 11 because both elements and text nodes are included in the resulting XMLList. XMLList provides a length method which can be used to find the number of contained elements:.

Note that unlike JavaScript arrays length is a method, not a property, and must be called using length. Here we are using identical syntax to that used to access numbered items in an array. We can also use the for each As with for E4X provides special operators for selecting nodes within a document that match specific criteria. These filter operations are specified using an expression contained in parentheses:. Nodes matching the path before the expression in this case the paragraph elements are added to the scope chain before the expression is evaluated, as if they had been specified using the with statement.

Consequently, filters can also run against the value of a single node contained within the current element:. E4X is fully namespace aware. Any XML object that represents a node or attribute provides a name method which returns a QName object, allowing easy inspection of namespaced elements. To access elements that are within a non-default namespace, first create a Namespace object encapsulating the URI for that namespace:.

This can now be used in E4X queries by using namespace::localName in place of a normal element specifier:. As of JavaScript 1. Get the latest and greatest from MDN delivered straight to your inbox. Sign in to enjoy the benefits of an MDN account. Last modified: Mar 23, , by MDN contributors. Learn the best of web development Get the latest and greatest from MDN delivered straight to your inbox.

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E4X Tutorial

ECMAscript for XML more colloquially known as E4X has had comparatively limited success of adoption in the face of the power of JSON, I suspect partially because of a general ambivalence that the JavaScript community has towards working with XML, but more so because there is comparatively little out there describing how best to take advantage of the features that E4X offers. E4X is an extension to JavaScript that is available to both Firefox and ActionScript developers that turns XML into a native data type on par with strings, arrays, objects, and regular expressions. It is not a DOM representation of XML, but rather is its own distinct entity, something that has its own set of associated methods and operators and that is intended to making it easier to work with XML than using the sometimes cumbersome methods associated with DOM perhaps the closest analogy I can think of would be the comparison between modeling clay with your bare hands and modeling clay with a waldo while wearing a space suit. There is a basic question that needs to be answered when addressing new technology. Objects have a few obvious advantages here, though the advantages are not as great as they may initially appear.

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E4X: JavaScript on steroids

This article or section is currently under construction. In principle, someone is working on it and there should be a better version in a not so distant future. If you want to modify this page, please discuss it with the person working on it see the "history". This article or section is a stub. It does not yet contain enough information to be considered a real article. In other words, it is a short or insufficient piece of information and requires additions. This text has been writting for casual E4X users by a a casual user.

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Processing XML with E4X

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