What does this page log in a 640px-wide browser viewport with the default 16px root font size?
HTML
<main class="layout"><article>Report</article><aside>Filters</aside></main>
<style>
.layout { display: grid; grid-template-columns: minmax(0, 1fr); }
@media (width >= 48rem) {
.layout { grid-template-columns: minmax(0, 1fr) 16rem; }
}
</style>
<script>
const value = getComputedStyle(document.querySelector('.layout')).gridTemplateColumns;
console.log(value.split(' ').length);
</script>