Toggle class with ES6 vanilla

vanilla.js

// The element you're targetting
// The class you're toggling

const el = document.querySelector('.menu-item-has-children');
const handleToggle = () => el.classList.toggle('available');
el.onclick = () => handleToggle();

document.addEventListener('click', event => {
  const isClickInside = el.contains(event.target)
  if (!isClickInside) {
    el.classList.remove('available')
  }
})