function toggleTheme() {

  var stylesheet = document.getElementById('stylesheet');

  if (stylesheet.getAttribute('href') === '/css/dark.css') {

    // update stylesheet and store
    stylesheet.setAttribute('href', '/css/light.css');
    localStorage.setItem('stylesheet', '/css/light.css');
    // update button emoji and store
    button = document.getElementById('toggle-button').innerText = '🌚'
    localStorage.setItem('button-emoji', '🌚');

  } else {

    // update stylesheet and store
    stylesheet.setAttribute('href', '/css/dark.css');
    localStorage.setItem('stylesheet', '/css/dark.css');
    // update button emoji and store
    button = document.getElementById('toggle-button').innerText = '🌞'
    localStorage.setItem('button-emoji', '🌞');

  }
}

window.addEventListener('load', function() {

  // get stored style
  var storedStyle = localStorage.getItem('stylesheet');
  var stylesheet = document.getElementById('stylesheet');
  // get stored emoji
  var storedEmoji = localStorage.getItem('button-emoji');
  var button = document.getElementById('toggle-button')

  // set stored style it exists
  if (storedStyle) {
    stylesheet.setAttribute('href', storedStyle);
  }
  // set stored emoji it exists
  if (storedEmoji) {
    button.innerText = storedEmoji;
  }
});