nixos-router/pkgs/router-webui/static/menu.js

// Menus close on a click elsewhere; forms with data-confirm ask first.
// Close an open menu when the click is somewhere else.
document.addEventListener("click", function (e) {
  document.querySelectorAll("nav details[open]").forEach(function (d) {
    if (!d.contains(e.target)) d.removeAttribute("open");
  });
});

// Ask before a form marked data-confirm is sent.
document.addEventListener("submit", function (e) {
  var q = e.target.getAttribute("data-confirm");
  if (q && !confirm(q)) e.preventDefault();
});