For example, I have some basic form:
var formElem = document.getElementById("some_basic_form");
formElem.onsubmit = async(e) => {
  e.preventDefault();
  let fullUrl = document.getElementById('shorten_url').value
  let formData = new FormData();
  formData.append('fullUrl', fullUrl);
  let response = await fetch('/url-shortenerer/create', {
    method: 'POST',
    body: formData
  });
  let result = await response.json();
  alert(result.message);
};<form action="http://localhost:8080" method="post" id="some_basic_form">
  Full url: <input id="shorten_url">
  <input type="submit">
</form>63342 port, not 8080. How to solve it? 
     
    