jQuery 없이 CSS와 JavaScript로 고정 헤더를 만드는 방법은 무엇입니까?

<code class="css">.sticky-header {
  width: 700px;
  height: 50px;
  background: orange;
  position: fixed;
}</code>

<code class="html"><div class="sticky"></div></code>

<code class="javascript">$(window).scroll(function() {
  var sticky = $('.sticky'),
    scroll = $(window).scrollTop();

  if (scroll >= 100) {
    sticky.addClass('fixed');
  } else {
    sticky.removeClass('fixed');
  }
});</code>

<code class="javascript">var stickyOffset = $('.sticky').offset().top;

$(window).scroll(function() {
  var scroll = $(window).scrollTop();

  if (scroll >= stickyOffset) {
    sticky.addClass('fixed');
  } else {
    sticky.removeClass('fixed');
  }
});</code>