Spot the bug - #109: Fade Transition

programming web dev
1

My fade-in animation just freezes halfway, any ideas?

function fadeIn(el) {
  let opacity = 0;
  function step() {
    opacity += 0.05;
    el.style.opacity = opacity;
    if (opacity < 1) {
      requestAnimationFrame(step);
    }
  }
  step;
}

fadeIn(document.querySelector('.box'));

Reply with what is broken and how you would fix it.