Syntax error : unexpected token: identifier

Question

I wish to display a mail icon with a counter

With my gnome-shell extension I get an error: I don't know what the error means. Keep in mind I do not have much knowledge about gnome..

Syntax error : unexpected token : identifier

    const INDICATOR_ICON = 'mail-unread-symbolic';
    const PanelMenu = imports.ui.panelMenu;
    const ExtensionUtils = imports.misc.extensionUtils;
    const Me = ExtensionUtils.getCurrentExtension();



class Extension extends PanelMenu.Button {
    _init() {
    super._init(0.0, null, false);
        this._icon = new St.Icon({
            icon_name: INDICATOR_ICON,
            style_class: 'system-status-icon'});

        this._iconBin = new St.Bin({ child: this._icon, x_fill: false, y_fill: false });
        
        this._counterLabel = new St.Label({ text: "0",
                                            x_align: Clutter.ActorAlign.CENTER,
                                            x_expand: true,
                                            y_align: Clutter.ActorAlign.CENTER,
                                            y_expand: true });
        
        this._counterBin = new St.Bin({ style_class: 'mailnag-counter',
                                        child: this._counterLabel,
                                        layout_manager: new Clutter.BinLayout() });
    
        this.add_actor(this._iconBin);
        this.add_actor(this._counterBin);
        
        
    
    }

   
}

function enable() {
  
   return New Extension();
  
}


function disable() {
  
}