使用XML数据库进行jQuery自动完成

Question

我正在尝试创建一个实现我创建的XML文件的自动完成搜索栏。我正在关注jQuery上的XML演示。我的脚本如下：

$(function() {
    function log( message ) {
        $( "<div/>" ).text( message ).prependTo( "#log" );
        $( "#log" ).attr( "scrollTop", 0 );
    }

    $.ajax({
        url: "courses.xml",
        dataType: "xml",
        success: function( xmlResponse ) {
            var data = $( "course", xmlResponse ).map(function() {
                return {    
                    value: $( "department_name", this ).text() + ", " +
                        ( $.trim( $( "class_number", this ).text() ) || "(unknown course)" ),
                    id: $( "id", this ).text()
                };
            }).get();

            $( "#results" ).autocomplete({
                source: data,
                minLength: 0,
                select: function( event, ui ) {
                    log( ui.item ?  
                        "Selected: " + ui.item.value + ", ID: " + ui.item.id :
                        "Nothing selected, input was " + this.value );
                }
            });
        }
    });
});

XML文件具有以下格式：

<courses>
<course id="1">
    <department_name>ELEC</department_name>
    <class_number>2001</class_number>
    <section_number>001</section_number>
    <professor>Chris, Michael</professor>
    <class_title>Electrical Engineering Concepts</class_title>
    <time_of_day>14:00-15:15</time_of_day>
    <days_of_week>TuTh</days_of_week>
    <building>Randalph Hall</building>
</course>   

搜索栏没有返回任何内容。没有自动完成功能。
感谢所有帮助