Javascript XML Parser wrapper

Question

I created an XML wrapper to easily access XML data. Please tell me what do you think about it.

• Performance
• Scalability
• Anything else...

This is how you use it:

var xml = new Xml(dataString);
xml.load("UserEmail");
alert(xml.length + ", " + xml.getValueAt(0)); // Out: 2, [email protected]

XML source file:

<Users>
 <Users>
 <UserEmail>[email protected]</UserEmail>
 <UserPassword>
 BA56E5E0366D003E98EA1C7F04ABF8FCB3753889
 </UserPassword>
 </Users>
 <Users>
 <UserEmail>[email protected]</UserEmail>
 <UserPassword>
 07B7F3EE06F278DB966BE960E7CBBD103DF30CA6
 </UserPassword>
 </Users>
</Users>

Source:

function Xml(xmlString) {
 var parser = function() {
 if (typeof window.DOMParser != "undefined") {
 return (new window.DOMParser()).parseFromString(xmlString,
 "text/xml");
 }
 else if (typeof window.ActiveXObject != "undefined"
 && new window.ActiveXObject("Microsoft.XMLDOM")) {
 var xmlDoc = new window.ActiveXObject("Microsoft.XMLDOM");
 xmlDoc.async = "false";
 xmlDoc.loadXML(xmlString);
 return xmlDoc;
 }
 else {
 throw new Error("XML parser not found");
 }
 };
 var data = parser(xmlString);
 var elements = null;
 this.length = 0;
 this.load = function(nodeName){
 elements = data.documentElement.getElementsByTagName(nodeName);
 this.length = elements.length;
 };
 this.getValueAt = function(index) {
 if(!elements || index >= this.length){
 return null;
 }
 var element = elements.item(index);
 return element.childNodes[0].data;
 };
}

• MaxArt: It can usefully handle very simple XMLs. It doesn't retrieve the value of attributes. It gives worthless values for element nodes. It doesn't support a decent selector engine. If it's good for your purposes, use it.
• David East: "Would you write your own XML Parser? Only if you're f***ing crazy." secretgeek.net/csv_trouble.asp
• Babibu: @David pmpl nice one ;)

Answer 1

From a quick read :

• Xml seems like a bad name for your wrapper, you should consider something like xmlParser ?

• I would allow access to data and elements by using this instead of var because you wrap so little of the XML parser API

• this.length seems wrong ( the parser has no length), maybe loadedElementCount, but even that is pretty bad, I would just let the caller use elements.length.

• I would return elements in this.load, since that is pretty much what the caller would need next.

• You are not checking for falsey values of nodeName in this.load

• I would not create a var element in getValueAt, I would just return elements.item(index).childNodes[0].data