blockscout/apps/block_scout_web/assets/js/pages/dark-mode-switcher.js

import $ from 'jquery'
import Cookies from 'js-cookie'

$('.dark-mode-changer').on('click', function () {
  if (Cookies.get('chakra-ui-color-mode') === 'dark') {
    Cookies.set('chakra-ui-color-mode', 'light')
  } else {
    Cookies.set('chakra-ui-color-mode', 'dark')
  }
  // reload each theme switch
  document.location.reload(true)
})