// Create a function that will handle any intersection between some elements and the viewport.

const handleHeaderIntersection = function (entries) {

  entries.forEach(entry => {

    if (entry.isIntersecting) {

      msgConsole('IntersectionObserver','The header is visible in the viewport');

      if (typeof headerIsNowVisible === 'function') headerIsNowVisible(entry);

    } else {

      msgConsole('IntersectionObserver','The header is invisible in the viewport');

      if (typeof headerIsNowInvisible === 'function') headerIsNowInvisible(entry);

    }

  });

}

const section_header = document.querySelector("header");

if (section_header) {

  const headerObserver = new IntersectionObserver(handleHeaderIntersection);

  if (headerObserver) headerObserver.observe(section_header);

} else myLog('No header to observe');