hamburger menu basic template

/*Downloaded from https://www.codeseek.co/codesnack/hamburger-menu-basic-template-PprVZG */
    .menu {
  max-height: 0;
  overflow: hidden;
  transition: .3s ease all;
  background: #222;
}
.menu a {
  display: block;
}

/*Downloaded from https://www.codeseek.co/codesnack/hamburger-menu-basic-template-PprVZG */
    var boton = document.querySelector("button");
var menu = document.querySelector("nav.menu");
var counter = 0;

boton.addEventListener("click", function(){
  if (counter === 0) {
      menu.style["max-height"] = "100px";
      counter = 1;
  } else {
    menu.style["max-height"] = 0;
    counter = 0;
  }
});