<form class="save-me" id="save-me">

  <label for="name">Name</label>
  <input type="text" name="name" id="name">

  <label for="address">Address</label>
  <input type="text" name="address" id="address">

  <label for="email">Email</label>
  <input type="email" name="email" id="email">

  <label for="more">Additional thoughts?</label>
  <textarea name="more" id="more"></textarea>

  <p>
    <button type="submit">Submit</button>
  </p>

</form>
 
<script>
  var storagePrefix = 'form-autosave_';

  var inputHandler = function (event) {
    if (!event.target.closest('#save-me')) return;

    var id = getID(event.target);
    if (!id) return;

    localStorage.setItem(storagePrefix + id, event.target.value);
  };

  var submitHandler = function (event) {
    if (event.target.id !== 'save-me') return;

    clearData();
  }

  var getID = function (field) {
    if (field.id.length > 0) {
      return field.id;
    }

    if (field.name.length > 0) {
      return field.name
    }
    return null;
  };

  var loadData = function () {
    // Get all of the form fields
    var fields = document.querySelectorAll('#save-me input, #save-me textarea');

    // Loop through each field and load any saved data in localStorage
    Array.prototype.slice.call(fields).forEach(function (field) {

      // If the field has no usable ID, skip it
      var id = getID(field);
      if (!id) return;

      // If there's no saved value in localStorage, skip it
      var saved = localStorage.getItem(storagePrefix + id);
      if (!saved) return;

      // Set the field value to the saved data in localStorage
      field.value = saved;

    });
  };

  var clearData = function () {

    // Get all of the form fields
    var fields = document.querySelectorAll('#save-me input, #save-me textarea');

    // Loop through each field and load any saved data in localStorage
    Array.prototype.slice.call(fields).forEach(function (field) {

      // If the field has no usable ID, skip it
      var id = getID(field);
      if (!id) return;

      // Remove the item from localStorage
      localStorage.removeItem(storagePrefix + id);

    });

  };

  loadData();
  document.addEventListener('input', inputHandler);
  document.addEventListener('submit', submitHandler);

</script>