javascript

Chapter 15: XML in JavaScript
(continued)
var result = doc.evaluate(expression, context, nsresolver,
XPathResult.ORDERED_NODE_SNAPSHOT_TYPE, null);
var nodes = new Array();
if (result !== null){
for (var i=0, len=result.snapshotLength; i < len; i++){
nodes.push(result.snapshotItem(i));
}
}
return nodes;
} else if (typeof context.selectNodes != “undefined”){
//create namespace string
if (namespaces instanceof Object){
var ns = “”;
for (var prefix in namespaces){
if (namespaces.hasOwnProperty(prefix)){
ns += “xmlns:” + prefix + “=’” + namespaces[prefix] + “’ “;
}
}
doc.setProperty(“SelectionNamespaces”, ns);
}
var result = context.selectNodes(expression);
var nodes = new Array();
for (var i=0,len=result.length; i < len; i++){
nodes.push(result[i]);
}
}
return nodes;
} else {
throw new Error(“No XPath engine found.”);
}
As you can see, much of the same logic is used from selectSingleNode() . In the DOM portion of the
code, an ordered snapshot result type is used and then stored in an array. To match the IE implementation,
the function should return an array even if no results were found, so the nodes array is always returned.
In the IE branch of the code, the selectNodes() method is called and then the results are copied into an
array. Since IE returns a NodeList , it ’ s best to copy the nodes over into an array, so the function returns
the same type regardless of the browser being used. This function can then be used as follows:
var result = selectNodes(xmldom.documentElement, “wrox:book/wrox:author”,
{ wrox: “http://www.wrox.com/” });
alert(result.length);
For the best cross - browser compatibility, it ’ s best to use these two methods exclusively for XPath
processing in JavaScript.
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