getElementZIndex.js

function getNonAutoZIndex(element) {
  if (!(element instanceof Element)) {
    console.warn("Invalid element provided.");
    return null;
  }

  const zIndex = window.getComputedStyle(element).zIndex;

  // Return the z-index value only if it is not 'auto'
  return zIndex !== 'auto' ? parseInt(zIndex, 10) : null;
}