options.js

// Saves options to browser.storage
function saveOptions() {
  var veggie = document.getElementById('veggie').value;
  const promise = browser.storage.sync.set({
    preferredVeggie: veggie,
  });
  promise.then(() => {
    // Update status to let user know options were saved.
    var status = document.getElementById('status');
    status.textContent = 'Options saved.';
    setTimeout(function() {
      status.textContent = '';
    }, 750);
  })
}

// Restores select box using the preferences stored in browser.storage.
function restoreOptions() {
  // Use default value veggie = 'sprouts'
  const promise = browser.storage.sync.get({
    preferredVeggie: 'sprouts'
  });  
  promise.then((items) => {
    console.log(items);
    document.getElementById('veggie').value = items.preferredVeggie;
  })
}

document.addEventListener('DOMContentLoaded', restoreOptions);
document.getElementById('save').addEventListener('click',
    saveOptions);