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Retrieving XML

As long as you include this code, you can use the

loadXML()

method in Mozilla the same way as in IE.

Retrieving XML

Remember that Microsoft’s XML DOM provides an

xml

property that allows easy access to the underly-

ing XML code. Because this property is not part of the standard, Mozilla doesn’t support it. Instead,

Mozilla has the

XMLSerializer

object, which is used for the same purpose:

var oSerializer = new XMLSerializer();

var sXml = oSerializer.serializeToString(oXmlDom, “text/xml”);

This simple code snippet creates the XML code for

oXmlDom

by using the

XMLSerializer

’s only

method:

serializeToString()

. The

serializeToString()

method accepts the node to serialize and

the content type as arguments. Once again, the content type can be

“text/xml”

“application/xml”

Using this object, it’s possible to synthesize the

xml

property for Mozilla using a little-known method

called

defineGetter()

The

defineGetter()

method exists only in Mozilla and is used to define a

getter function

for a property,

meaning that when the property is accessed in read mode, this function is called and the return value is

assigned to the property. For example:

var sValue = oXmlNode.nodeValue; //read mode

oXmlNode.nodeValue = “New value”; //write mode

The first line of code uses the

nodeValue

property in read mode, meaning that the interpreter is reading

the value from the property. If a getter function is defined, it is run and its value returned. The second

line of code uses

nodeValue

in write mode, meaning that a value is being assigned to it. If a

setter func-

tion

is defined (the opposite of a getter function), then it is called with

New value

as an argument. Yes,

there is also a

defineSetter()

method, but it’s unnecessary here.

This method,

defineGetter()

, is hidden by using the JavaScript standard for private properties and

methods — using double underscores before and after the name:

oObject.__defineGetter__(“propertyName”, function() { return “propertyValue”; });

As you can see,

defineGetter()

takes two arguments: the name of the property and the function to

call. Whatever you specify as the property name cannot be used as a regular property. For example, you

should never do this:

oObject.propertyName = “blue”;

oObject.__defineGetter__(“propertyName”, function() { return “propertyValue”; });

Typically getter and setter functions are defined in pairs, although you can effectively create a read-only

property by assigning just a getter. This is way to create the

xml

property.

This code will cause an error in IE, where no

Document

object exists. To prevent this,

use a browser detect around the code.

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XML in JavaScript

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