uswds/src/js/utils/is-in-viewport.js

Open source UI components and visual style guide for U.S. government websites

// https://stackoverflow.com/a/7557433
function isElementInViewport(el, win = window,
  docEl = document.documentElement) {
  const rect = el.getBoundingClientRect();

  return (
    rect.top >= 0
    && rect.left >= 0
    && rect.bottom <= (win.innerHeight || docEl.clientHeight)
    && rect.right <= (win.innerWidth || docEl.clientWidth)
  );
}

module.exports = isElementInViewport;