function jsSubmit(event) {
  const form = event.target
  const formData = new FormData(form);
  const data = Object.fromEntries(formData)
  
  fetch(form.action, {
    method: form.method,
    body: new URLSearchParams(data)
  })
  
  event.preventDefault()
}

document.querySelector('form').addEventListener('submit', jsSubmit)