在Node.js车把模板中选择的下拉列表设置选项值

Question

我有一个Handlebars.js模板，如下所示，我需要将option值设置为从nodejs呈现的数据中动态选择的值

    <select class="form-control" name="c_level" value="{{course.c_level}}" required>
        {{#levelc course.c_level}}
            {{#each level}}  
            <option value="{{this.level}}" name = "c_level">{{this.level}}</option>
            {{/each}}
        {{/levelc}}
    </select>

以上代码的输出为

    <select class="form-control" name="c_level" value="C Level" required="">
        <option value="C Level" selected="">C Level</option>  
        <option value="Safety" name="c_level">Safety</option>
        <option value="D Level" name="c_level">D Level</option>
        <option value="C Level" name="c_level">C Level</option>
        <option value="B Level" name="c_level">B Level</option>
        <option value="A Level" name="c_level">A Level</option>
        <option value="Customer Courses" name="c_level">Customer Courses</option>
        <option value="Special Courses" name="c_level">Special Courses</option>
    </select>

我的助手js文件是

    Handlebars.registerHelper('levelc', function( value, options ){
            var $el = $('<select />').html( options.fn(this) );
            $el.find('[value="' + value + '"]').attr({'selected':'selected'});
            return $el.html();
        });

我的声明了助手的服务器js文件是

    const exphbs = require('express-handlebars');
    app.engine('hbs', exphbs({ extname: 'hbs', helpers: require("./helpers/handlebars").helpers, defaultLayout: 'mainLayout', layoutsDir: __dirname + '/views/layouts/' }));

该html部分的预期输出是应将选择属性“ C Level”的值设置为该选项上的选定值

        <select class="form-control" name="c_level" value="C Level" required=""> 
        <option value="Safety" name="c_level">Safety</option>
        <option value="D Level" name="c_level">D Level</option>
        <option value="C Level" name="c_level" selected>C Level</option>
        <option value="B Level" name="c_level">B Level</option>
        <option value="A Level" name="c_level">A Level</option>
        <option value="Customer Courses" name="c_level">Customer Courses</option>
        <option value="Special Courses" name="c_level">Special Courses</option>
    </select>

我收到一条错误消息，我无法在两天内弄清楚

  (function (exports, require, module, __filename, __dirname) { 
  Handlebars.registerHelper('levelc', function( value, options ){
                                                          ^

     ReferenceError: Handlebars is not defined