Component toggle not toggling

I used this toggler to add a class to an element if checked. Maybe your goal is the same with a class for a larger font. I used it like this:

checked: !!textSize,
onChange: function(){
                textSize ? props.setAttributes({ textSize: '' }) : props.setAttributes({ textSize: ' big' })
                    }

So textSize controls the checked status and holds the classname, if checked. You can use the textSize string in other elements className: attributes.