const form = document.getElementById('reading-form');
form.addEventListener('submit', e => {
  e.preventDefault();
  const data = {
    dockDoor: +document.getElementById('dockDoor').value,
    timestamp: document.getElementById('timestamp').value,
    temperature: +document.getElementById('temperature').value,
    humidity: +document.getElementById('humidity').value,
  };
  fetch('/api/readings', {
    method: 'POST', headers: { 'Content-Type': 'application/json' }, body: JSON.stringify(data)
  }).then(res => res.json()).then(() => form.reset());
});