index-main/assets/js/investigation.js

export function navInvestigation(){
  const nav = document.getElementById('nav-investigation');
  if (!nav) return;

  const items = nav.querySelectorAll('li');
  const headerOffset = parseInt(getComputedStyle(document.documentElement).getPropertyValue('--h-header')) || 0;

  const sections = Array.from(items).map(li => {
    const href = li.querySelector('a')?.getAttribute('href');
    const target = href ? document.querySelector(href) : null;
    return { li, target };
  }).filter(s => s.target);

  const update = () => {
    const scrollY = window.scrollY + headerOffset;
    let current = sections[0];

    for (const section of sections) {
      if (section.target.offsetTop <= scrollY) {
        current = section;
      }
    }

    items.forEach(li => li.classList.remove('is-selected'));
    if (current) current.li.classList.add('is-selected');
  };

  window.addEventListener('scroll', update, { passive: true });
  update();
}