What's wrong with this code? (TineMCE)

Hey,
I’m trying to make a button that when it clicked, it wrap some text with shortcodes.
Everything went good and I did this button, but now, I want to go to the next step which is to make the button a menu button, with several options inside it. but for some reason, it doesn’t work.
This is the js. code that does work:

(function() {
    tinymce.create('tinymce.plugins.dropcapButton', {
        init : function(ed) {
            ed.addButton('dropcap', {
                title : 'testMenuButton',
                icon : 'icon dashicons-wordpress-alt',
                cmd:"dropcap"
            });
            ed.addCommand("dropcap", function() {
                var selected_text = ed.selection.getContent();
                var return_text = '';
                return_text = '[col-num]' + selected_text + '[/col-num]';
                ed.execCommand('mceInsertContent', 0, return_text);
            });
        },
    });
    // Register plugin
    tinymce.PluginManager.add( 'dropcap', tinymce.plugins.dropcapButton );
})();

But when I try this one, simply nothing happens when I press the button inside the main button.

(function() {
    tinymce.create('tinymce.plugins.dropcapButton', {
        init : function(ed) {
            ed.addButton('dropcap', {
                title : 'testMenuButton',
                type : 'menubutton',
                icon : 'icon dashicons-wordpress-alt',
                menu : [{
                	text : "1",
                	title : 'DropCap',
                	cmd : "dropcap",
                	icon : 'icon dashicons-wordpress-alt'
                }]
            });
            ed.addCommand("dropcap", function() {
                var selected_text = ed.selection.getContent();
                var return_text = '';
                return_text = '[col-num]' + selected_text + '[/col-num]';
                ed.execCommand('mceInsertContent', 0, return_text);
            });
        },
    });
    // Register plugin
    tinymce.PluginManager.add( 'dropcap', tinymce.plugins.dropcapButton );
})();

Thanks in advance!