Custom panel is not a constructor issue.

initialize a panel with ExtJS 3.4

Code:

custom.CustomPanel = Ext.extend(Ext.Panel, {
            constructor: function(config) {
            config = config || {};
            Ext.apply({
                    layout: 'form',
                    labelAlign: 'left',
                    defaultType: 'textfield',
                    width: 600,
                    height: 500,
                    items: [
                            grid
                        ],
            }, config );
            custom.CustomPanel.superclass.constructor.call(this, config);
        };
    })

and implementing with this way

Code:

some.elseCustomPanel = new custom.CustomPanel({
                    region:'center',
                    border: '1px'
            });

and gives error `custom.CustomPanel` is not a constructor

what I am missing?

Custom panel is not a constructor issue.