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<!DOCTYPE html>
<html lang="en">
<head>
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<style>
body {
margin: 0;
height: 100%;
}
.app {
display: flex;
width: 100%;
}
.sidebar {
width: 31.1%;
margin: 0;
background: rgb(231, 249, 139);
}
section {
width: 68.9%;
background-color: rgb(119, 219, 172);
border: dashed red 3px;
}
p {
margin-top: 0;
}
</style>
</head>
<body>
<div class=app>
<div class="sidebar"></div>
<section id=target>
<h2>Observer target</h2>
<p><strong>Intersection ratio:</strong> <span id=ratio></span></p>
</section>
</div>
<script>
const onIntersection = entries => {
const ratio = entries[0].intersectionRatio;
const eventData = { intersectionRatio: ratio };
document.getElementById("ratio").innerText = ratio.toFixed(5);
const event = new CustomEvent("iframeObserved", {detail: eventData});
parent.document.dispatchEvent(event);
};
const observer = new IntersectionObserver(onIntersection, {threshold: 1});
setTimeout(() => {observer.observe(document.getElementById("target"))}, 0);
</script>
</body>
</html>