Uncaught TypeError: undefined is not a function

Hi All,

I have the following widget template:

            template:
                '<div class="testwidget">' +
                    '<div class="testwidget-title">$title</div>' +
                    '<div class="testwidget-desc">$description</div>' +
                    '<div id="config">' + 
                    '</div>' +
                 '</div>',

            button: 'Create a test widget',

In the data method I want to append an input element something like the following

<input type="hidden" id="tag" value="test">

            data: function() {
                var ele = editor.document.createElement( 'input' );
                ele.setAttribute('type', 'hidden');
                ele.setAttribute('id', 'tag');
                ele.setAttribute('value', this.data.tag);
                var configObj = this.element.find('div#config');
                configObj.append(ele);

The above code retrieves the configObj correctly, but is unable to append the input element to config div. The last line throws an error

Uncaught TypeError: undefined is not a function

How can I append html to widget content dynamically?

Thanks

Ashy