webs
/
test_scroll.html

<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
		<style type="text/css">
			#app{height: 100px; overflow-y: scroll; border: 1px solid #ff0000;}
			.child{height: 50px; background: #eeeeee;}
		</style>
	</head>
	<body>
		<div id="app" onscroll="myfuc()">
			<div class="child">1</div>
			<div class="child">2</div>
			<div class="child">3</div>
		</div>

		<div></div>
		<script>
			let app = document.getElementById('app');
			console.log(app.offsetHeight,'offsetHeight');
			console.log(app.clientHeight,'clientHeight');
			console.log(app.scrollHeight,'scrollHeight')
			function myfuc(){
				console.log(app.scrollTop,'scrollTop')
			}
		</script>
	</body>
</html>