unit-vh-vw-overflow-scroll-y-ref-iframe.html
<style>
body { overflow-y: scroll }
div {
width: 10px;
height: 10px;
background-color: #d64203;
}
</style>
<body>
<div id="a"></div>
<div style="height: 50px"></div> <!-- Unaffected by scrollbars. -->
<div id="c"></div>
<div style="height: 50px"></div> <!-- Unaffected by scrollbars. -->
<!-- Deliberately make scrollbars appear. -->
<div style="width: 500px; height: 500px; background-color: black">
</body>
<script>
// client{Width, Height} consist of the area _inside_ the scrollbars, so these
// manually calculated units reflect the fact that with 'overflow: scroll' set,
// viewport units are sized taking the scrollbars into account. Since we're
// only dealing with 'overflow-y' here, only the width units are affected.
var vw = 0.01 * document.body.clientWidth;
document.getElementById('a').style.width = (50 * vw) + "px";
document.getElementById('c').style.width = (35 * vw) + "px";
</script>
