css/css-grid/grid-items/grid-item-rel-pos-001.html

<!DOCTYPE HTML>
<meta charset="utf-8">
<title>CSS Grid Layout Test: Rel.pos. grid item with style change.</title>
<link rel="author" title="James0x57" href="mailto:James0x57@gmail.com">
<link rel="author" title="Mats Palmgren" href="mailto:mats@mozilla.com">
<link rel="help" href="http://www.w3.org/TR/css-grid-1/#grid-items" title="Grid Items">
<link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1576355">
<link rel="match" href="grid-item-rel-pos-001-ref.html">
<meta name="assert" content="Checks that the rel.pos. grid items are positioned correctly after a 'left' style change.">
<style>
.grid {
  margin: 40px;
  display: grid;
  grid: auto / repeat(3,100px);
  grid-gap: 20px;
}
span, even {
  position: relative;
  min-height: 20px;
  background: grey;
  left: 0px;
}
.offset even {
  left: 50%;
}

</style>


<div class="grid offset">
  <span></span><span></span><span></span>
  <even></even><even></even><even></even>
  <span></span><span></span><span></span>
</div>

<script>
  document.body.offsetHeight;
  let grid = document.querySelector('.grid');
  grid.classList.remove('offset')
  document.body.offsetHeight;
  grid.classList.add('offset')
</script>