css/css-scroll-snap/ignore-snap-points-orthogonal-to-snap-axis.html

<!DOCTYPE html>
<title>Ignore snap points orthogonal to scroll snap axis</title>
<link rel="help" href="https://drafts.csswg.org/css-scroll-snap/#snap-axis" />
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<style>
div {
  position: absolute;
  margin: 0;
}

#scroller {
  height: 500px;
  width: 500px;
  overflow: hidden;
  scroll-snap-type: x mandatory;
}

#y-target {
  width: 300px;
  height: 300px;
  top: 100px;
  left: 0;
  background-color: green;
  /* align only on y-axis */
  scroll-snap-align: start none;
}

#x-target {
  width: 300px;
  height: 300px;
  top: 0;
  left: 100px;
  background-color: red;
  scroll-snap-align: none start;
}

.area {
  width: 2000px;
  height: 2000px;
}
</style>

<div id="scroller">
  <div class="area"></div>
  <div id="x-target"></div>
  <div id="y-target"></div>
</div>

<script>
test(t => {
  scroller.scrollTo(0,0);
  assert_equals(scroller.scrollTop, 0);
  assert_equals(scroller.scrollLeft, 100);
}, "Ignore snap points orthogonal to scroll snap axis");

</script>