On page 536 this code exists (this is just the relevant snippet of that code):

if (namespaces instanceof Object){
nsresolver = function(prefix){
return namespaces[prefix];
};
}
var result = doc.evaluate(expression, context, nsresolver,
XPathResult.FIRST_ORDERED_NODE_TYPE, null);

I don't understand where the function parameter 'prefix' is coming from, at no point is this parameter being filled with any data that the function can work with when it is being called.

Thanks

Prefix is passed in as part of document.evaluate(). When this method encounters a namespace prefix, it runs the namespace resolver function and passes in the namespace prefix to be resolved.

__________________
Nicholas C. Zakas
Author, Professional JavaScript for Web Developers (ISBN 0764579088)
http://www.nczonline.net/