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XPathResult

The third argument, the namespace resolver, is necessary only when the XML code uses an XML names-

pace, and so typically is left as

null

. The fourth argument, the type of result to return, is one of 10 con-

stants values:

XPathResult.ANY_TYPE

— Returns the type of data appropriate for the XPath expression

XPathResult.ANY_UNORDERED_NODE_TYPE

— Returns a node set of matching nodes,

although the order may not match the order of the nodes within the document

XPathResult.BOOLEAN_TYPE

— Returns a Boolean value

XPathResult.FIRST_ORDERED_NODE_TYPE

— Returns a node set with only one node, which

is the first matching node in the document

XPathResult.NUMBER_TYPE

— Returns a number value

XPathResult.ORDERED_NODE_ITERATOR_TYPE

— Returns a node set of matching nodes in

the order in which they appear in the document. This is the most commonly used result type.

XPathResult.ORDERED_NODE_SNAPSHOT_TYPE

— Returns a

node set snapshot

, capturing the

nodes outside of the document so that any further document modification doesn’t affect the

node list. The nodes in the node set are in the same order as they appear in the document.

XPathResult.STRING_TYPE

— Returns a string value

XPathResult.UNORDERED_NODE_ITERATOR_TYPE

— Returns a node set of matching nodes,

although the order may not match the order of the nodes within the document

XPathResult.UNORDERED_NODE_SNAPSHOT_TYPE

— Returns a node set snapshot, capturing the

nodes outside of the document so that any further document modification doesn’t affect the node

set. The nodes in the node set are not necessarily in the same order as they appear in the document.

The type of result you specify determines how to retrieve the value of the result. Here’s a typical example:

var oEvaluator = new XPathEvaluator();

var oResult = oEvaluator.evaluate(“employee/name”, oXmlDom.documentElement, null,

XPathResult.ORDERED_NODE_ITERATOR_TYPE, null);

if (oResult != null) {

var oElement = oResult.iterateNext();

while(oElement) {

alert(oElement.tagName);

oElement = oResult.iterateNext();

}

This example uses the

XPathResult.ORDERED_NODE_ITERATOR_TYPE

result, which is the most com-

monly used result type. If no nodes match the XPath expression,

evaluate()

returns

null

; otherwise, it

returns an

XPathResult

object. If the result is a node iterator, whether it be ordered or unordered, you

use the

iterateNext()

method repeatedly to retrieve each matching node in the result. When there are

no further matching nodes,

iterateNext()

returns

null

. Using a node iterator, it’s possible to create a

selectNodes()

method for Mozilla:

Element.prototype.selectNodes = function (sXPath) [

var oEvaluator = new XPathEvaluator();

var oResult = oEvaluator.evaluate(sXPath, this, null,

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