spa-approach.js

const scripts = [
  'https://example.com/script1.js',
  'https://example.com/script2.js',
];
const registrations = {};

function activityCheck(name) {
  const current = location.hash;
  const registration = registrations[name];

  if (registration) {
    if (registration.activity(current) !== registration.active) {
      if (registration.active) {
        registration.lifecycle.unmount();
      } else {
        registration.lifecycle.mount();
      }

      registration.active = !registration.active;
    }
  }
}

window.addEventListener('hashchange', function () {
  Object.keys(registrations).forEach(activityCheck);
});

window.registerApp = function(name, activity, lifecycle) {
  registrations[name] = {
    activity,
    lifecycle,
    active: false,
  };
  activityCheck(name);
}

scripts.forEach(src => {
  const script = document.createElement('script');
  script.src = src;
  document.body.appendChild(script);
});