如何居中div？

div {
  text-align: center;
}

div {
  margin: 0 auto;
}

div {
  display: flex;
  justify-content: center;
  align-items: center;
}

function centerDiv() {
  const div = document.querySelector('div');
  const parent = div.parentNode;
  const parentWidth = parent.offsetWidth;
  div.style.left = `${parentWidth / 2 - div.offsetWidth / 2}px`;
}