Undefined element of forEach inside if condition [closed]

I try to make next code:

if(parseInt(e.target.value) === 1){            
            e.target.nextSibling.childNodes.forEach(element => {
                element.classList.add('disable')
            });            
        }
        else if(parseInt(e.target.value) === 2){
            e.target.nextSibling.childNodes.forEach(element,index => {
                index === 0 ?
                element.classList.remove('disable')
                :element.classList.add('disable')
            });
        }

and in second condition it throw me error 'element' is not defined but in first it works fine. But I cant understand why if statment make my element is undefined?