function handleSticky() {
  if (window.scrollY >= window.innerHeight * 0.65) {
    document.querySelector('header').setAttribute('data-header-visible', true);
  } else {
    document.querySelector('header').setAttribute('data-header-visible', false);
  }
}
window.onload = function () {
  this.handleSticky();
  window.addEventListener('scroll', this.handleSticky);
};