How to generate a XML from XML in jQuery (Javascript)?

I'm trying to generate a XML from client side XML according to this link. But it isn't work. Here is my js code:

// XML Builder
$.createElement = function(name)
{
    return $('<'+name+' />');
};

$.fn.appendNewElement = function(name)
{
    this.each(function(i)
    {
        $(this).append('<'+name+' />');
    });
    return this;
}

generateXMLFromXML(1);

function generateXMLFromXML(id)
{
    var $root = $('<?xml version="1.0" encoding="utf-8" ?>');

    $root.append(
        $('row').append (
                $('page').text(1)
        )
    );
    console.log($.isXMLDoc($root)); // return false
    $root.find('page').each(function(){
        console.log($(this).text());
    });
}