XML Demystified

CHAPTER 10 MSXML
The first four lines of the InsertBefore() function are the same as those for the
InsertFirst() and InsertLast() functions.
Line five calls the selectNodes() method of the DOMDocument object. This
method requires one argument containing an XPath expression (see Chapter 5) to
identify the node that will come after the new CD in the XML document.
This expression says, Look in the /catalog element for a cd element whose upc
attribute is equal to the UPC passed to the selectNodes() method. There can be
more than one match. Therefore, the selectNodes() method returns a collection that
contains references of matching nodes.
Line six evaluates the value of the length property of the node list returned by the
selectNodes() method. If the length is zero, then the CD entered by the user can’t
be located in the XML document and an alert message is displayed; then the function
returns to the statement that called it.
Line seven executes if the selectNodes() method returned a node indicating that
the CD was found in the XML document. Line seven calls the insertBefore()
method, which is also called by the InsertFirst() function and InsertLast() function.
The insertBefore() method requires two arguments. The first argument references
the new CD and the second argument references the first CD that will come after
the new CD in the XML document. The second argument is the first node the
collection returned by the selectNodes() method.
Line eight is the same as it was in the previous functions.
Here’s the XML document after the InsertBefore() function executes:
U2
How to Dismantle an Atomic Bomb
13.98
Interscope Records
2004-11-23
Led Zeppelin
Physical Graffiti
22.99
Atlantic
1994-08-16
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