'use strict';

window.addEventListener('scroll', () => {
  const articles = document.getElementsByTagName('article');
  const header = document.getElementById('side-bar');

  if (window.pageYOffset >= 500) {
    if (header && !header.classList.contains('hidden')) {
      header.classList.add('hidden');

      if (articles) {
        [...articles].forEach(e => {
          e.classList.add('zen-mode');
        });
      }
    }
  } else if (header && header.classList.contains('hidden')) {
    header.classList.remove('hidden');
    if (articles) {
      [...articles].forEach(e => {
        e.classList.remove('zen-mode');
        e.classList.add('zen-mode-disabling');
      });
      setTimeout(function() { 
        [...articles].forEach(e => {
          e.classList.remove('zen-mode-disabling');
        });
      }, 1000);
    }
  }
});