const btn = document.querySelectorAll(".botao");
const txt = document.querySelector(".txtTelefone");
const btnapagar = document.querySelector(".btnApagar");
for(let i = 0; i<btn.length; i++){
const botoes = btn[i];
const value = botoes.value;
botoes.addEventListener('click', function () {
txt.value = txt.value+value;
});
}
btnapagar.addEventListener('click', function(){
txt.value = "";
}); 
