summernote自定义下拉列表按钮

var SequenceButton = function (context) {
    var ui = $.summernote.ui;
    var button = ui.buttonGroup([
        ui.button({
            contents: '<i class="note-icon-special-character" />    <span class="caret"></span>',
            tooltip: '插入序号',
            data: {
                toggle: 'dropdown'
            }
        }),
        ui.dropdown({
            items: ['①', '②', '③', '④', '⑤', '⑥','⑦','⑧','⑨'],
            callback: function (items) {
                $(items).find('li a').on('click', function () {
                    context.invoke("editor.insertText", $(this).html());
                });
            }
        })
    ]);

    return button.render();
};