text-display/public/js/edit.js

function saveText() {
  let x = document.getElementById("text").value;

  const options = {method: 'POST', body: JSON.stringify({text: x}), headers: { 'Content-Type': 'application/json' }};

  fetch(location.protocol + '/api/edit', options)
    .then((response) => response.text())
    .then(data => {
        redirectOrNot(data);
    })
    .catch(err => console.error(err));
}

async function redirectOrNot(res) {
  let url = location.protocol
  location.href = url+res
}