javascript

Chapter 15: XML in JavaScript
namespace — if namespaces aren ’ t used, this should be set to null . The fourth argument, the type of
result to return, is one of the following 10 constants values:
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XPathResult.ANY_TYPE — Returns the type of data appropriate for the XPath expression.
XPathResult.NUMBER_TYPE — Returns a number value.
XPathResult.STRING_TYPE — Returns a string value.
XPathResult.BOOLEAN_TYPE — Returns a Boolean 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.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.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.
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
result set. The nodes in the result set are in the same order as they appear in the document.
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.FIRST_ORDERED_NODE_TYPE — Returns a node set with only one node, which is
the first matching node in the document.
The type of result you specify determines how to retrieve the value of the result. Here ’ s a typical
example:
var result = xmldom.evaluate(“employee/name”, xmldom.documentElement, null,
XPathResult.ORDERED_NODE_ITERATOR_TYPE, null);
if (result !== null) {
var node = result.iterateNext();
while(node) {
alert(node.tagName);
node = node.iterateNext();
}
}
This example uses the XPathResult.ORDERED_NODE_ITERATOR_TYPE result, which is the most
commonly used result type. If no nodes match the XPath expression, evaluate() returns null ;
otherwise, it returns an XPathResult object. The XPathResult has properties and methods for
retrieving results of specific types. If the result is a node iterator, whether it be ordered or unordered, the
iterateNext() method must be used to retrieve each matching node in the result. When there are no
further matching nodes, iterateNext() returns null .
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