ActionScript for Flash MX: The Definitive Guide, Second Edition

XML.getBytesLoaded() Method

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Alphabetical Language Reference

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Description

The firstChild property is synonymous with childNodes[0]. It returns a reference to the

first node object that descends from

theNode, where theNode can be an XML or XMLnode

instance. If

theNode has no children, firstChild returns null.

In this XML source fragment, the

firstChild of the MESSAGE node is the text node with the

nodeValue “hey”:

<!-- Fragment 1 -->

<MESSAGE>hey</MESSAGE>

Here, the firstChild of the HOTEL node is the ROOM node:

<!-- Fragment 2 -->

<HOTEL><ROOM><SIZE>Double</SIZE></ROOM></HOTEL>

When theNode is the top of the object hierarchy (i.e., when it is an instance of the XML

class, which refers to an XML document object and not an instance of the XMLnode class),

firstChild may not always be a reference to the first useful element in the document. If a

document includes an XML declaration (

<?xml version="1.0"?>) and perhaps a DOCTYPE tag,

normally there are whitespace nodes before the actual root element of the XML hierarchy

(to remove them, use

XML.ignoreWhite). If an XML fragment has no XML declaration, no

DOCTYPE, and no whitespace, we can start processing it with the document’s firstChild

node, as in:

// Create a new XML fragment

myDoc = new XML('<MESSAGE><USER>gray</USER><CONTENT>hi</CONTENT></MESSAGE>'); ...