XMLCreator.js

   var XMLCreatorFactory = function(dom, resolver) {
     if (dom === true) {
       dom = document.implementation.createDocument('', '', null);
     } else if (!(dom instanceof Document)) {
       dom = document;
     }

     var lookupNamespaceURI;
     if (resolver instanceof Function && !resolver.lookupNamespaceURI instanceof Function) {
       lookupNamespaceURI = resolver;
     } else if (resolver && resolver.lookupNamespaceURI instanceof Function) {
       lookupNamespaceURI = resolver.lookupNamespaceURI;
     } else {
       lookupNamespaceURI = function(namespaces) {
         namespaces = (namespaces instanceof Object) ? namespaces : {};
         return function(prefix) {
           if (prefix == '') {
             return null;
           }
           return namespaces[prefix] || null;
         };
       }(resolver);
     }

     var getNamespace = function(nodeName) {
       if (nodeName.indexOf(':') > -1) {
         prefix = nodeName.substr(0, nodeName.indexOf(':')) || '';
       } else {
         prefix = '#default';
       }
       return lookupNamespaceURI(prefix);
     };

     var appendTo = function(target, value) {
       var i;
       if (value instanceof Node) {
         node.appendChild(value.cloneNode(true));
       } else if (value instanceof Array) {
         for (i = 0; i < value.length; i++) {
           appendTo(target, value[i]);
         }
         node.appendChild(dom.createTextNode(value));
       } else if (value instanceof Object){
         for (i in value) {
           if (!value.hasOwnProperty(i)) { continue; }
           node.setAttributeNS(getNamespace(i), i, value[i]);
         }
       } else if (typeof value == 'string') {
         node.appendChild(dom.createTextNode(value.toString()));
       }
     };

     var XMLCreator = function(name) {
       node = dom.createElementNS(getNamespace(name), name);
       for (var i = 1; i < arguments.length; i++) {
         appendTo(node, arguments[i]);
       }
       return node;
     };

     XMLCreator.cdata = function(content) {
       return dom.createCDATASection(content);
     };

     XMLCreator.comment = function(content) {
       return dom.createComment(content);
     };

     XMLCreator.pi = function(content) {
       return dom.createProcessingInstruction(content);
     };

     return XMLCreator;
   };

   var $_;
   $_ = XMLCreatorFactory();
   console.log(
     $_(
       'ul',
       $_('li', 'bar', {class : 'foo'})
     )
   );

   $_ = XMLCreatorFactory(true, {atom : 'urn:atom'});
   console.log(
     $_(
       'atom:feed',
       $_('atom:title', 'bar'),
       $_.cdata('test')
     )
   );