ActionScript: The Definitive Guide

Name

XML.firstChild Property — a reference to the first descendant of a node

Availability

Flash 5

Synopsis

theNode.firstChild

Access

Read-only

Description

The firstChild property is synonymous with childNodes[0]. It returns a reference to the first node object that descends from theNode. 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., refers to the XML document object), firstChild may not always be a reference to the first useful element in the document. If a document includes an XML delcaration (<?xml version="1.0"?>) and perhaps a DOCTYPE tag, there are normally whitespace nodes before the actual root element of the XML hierarchy. However, if an XML fragment has no XML declaration and no DOCTYPE, 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>');

// Store the XML fragment's first node in the variable msg
msg = myDoc.firstChild;

// Assign the text contained by the USER tag
// to a text field called userNameOutput
userNameOutput = msg.firstChild.firstChild.nodeValue;

It’s good form, but not actually necessary, to use nodeValue to access the ...