Wikipedia: Vorschaubilder per Klick vergrößern

// Click a thumbnail to enlarge it inline without opening the file page
function setupThumbZoom() {
  const imgs = document.querySelectorAll('.mw-parser-output .thumb img');
  imgs.forEach(function (img) {
    if (img.dataset.jzZoom) { return; }
    img.dataset.jzZoom = '1';
    img.style.cursor = 'zoom-in';
    img.addEventListener('click', function (e) {
      e.preventDefault();
      e.stopPropagation();
      const big = img.dataset.jzBig === '1';
      img.style.maxWidth = big ? '' : '100%';
      img.style.width = big ? '' : 'auto';
      img.style.height = big ? '' : 'auto';
      img.style.transform = big ? '' : 'scale(1)';
      img.style.cursor = big ? 'zoom-in' : 'zoom-out';
      img.dataset.jzBig = big ? '0' : '1';
    }, true);
  });
}
setupThumbZoom();
new MutationObserver(setupThumbZoom).observe(document.body, { childList: true, subtree: true });