const change_state = (a,b) => {
    return () => {
        if(a.style.display === "block"){
            a.style.display = "none"
            b.style.display = "block"
        }else{
            a.style.display = "block"
            b.style.display = "block"
        }
    }
}

santaa.onclick = change_state(santaa,santac)
santac.onclick = change_state(santac,santaa)