Question: ```
    someClass = Ext.extend(someClassB, {
        _someFunctionC{  
           someButton = new Ext.button({  
              handler: function () {
                            this._onClick('click');
                       }
           }),
           _onClick(someMessage){
               Ext.Msg.alert(someMessage);
            }
        }
    }

```

\_onClick eats one parameter; in the above code you put in the 'click' event because you want \_onClick to be executed after the user clicks on the button. However, how do you specify this specific 'click' registration AND pass in a local variable as the \_onClick parameter at the same time?

As an aside, why do you even have to specify 'click', when the API states that handler always pertains to a click? Is this additional information not unnecessary?

Answer: 
So if i understand correctly you want to set the handler config option but set the arguments yourself in one go?

Does this do what you want?

```
// clicking the button alerts 'Hello World'
new Ext.Button({
    text: 'Test',
    handler: function(value){
        alert('Hello, ' + value);
    }.createCallback('World')
});

```

Notice the `createCallback` executed on the anonymous function, this creates a callback function for `handler` which only gets passed the arguments you pass to `createCallback`.
You can also create a callback function that inserts extra parameters when it is called:

```
var button = new Ext.Button({
    handler: this.someFunction.createDelegate(button,['Some message'])
});

```