BRC A+

const updateHeaderMetrics = () => { const header = document.getElementById('header'); const rect = header.getBoundingClientRect(); const headerHeight = rect.bottom; document.documentElement.style.setProperty('--header-height', `${headerHeight}px`); }; window.addEventListener('DOMContentLoaded', updateHeaderMetrics); window.addEventListener('resize', updateHeaderMetrics); const header = document.getElementById('header'); const resizeObserver = new ResizeObserver(entries => { for (let entry of entries) { const rect = entry.target.getBoundingClientRect(); const headerHeight = rect.bottom; document.documentElement.style.setProperty('--header-height', `${headerHeight}px`); } }); resizeObserver.observe(header);

BRC A+