CSS+JS 置顶效果

阿里云国内75折回扣微信号：monov8

阿里云国际，腾讯云国际，低至75折。AWS 93折免费开户实名账号代冲值优惠多多微信号：monov8 飞机：@monov6

置顶效果

在这里插入图片描述

<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title>置顶效果</title>
		<style type="text/css">
			body {
				height: 5000px;
			}

			img {
				position: fixed;
				right: 50px;
				bottom: 50px;
				width: 80px;
				display: none;
				cursor: pointer;
			}
		</style>
	</head>
	<body>
		<h3>hello world</h3>
		<div><img src="../img/toTop.png" alt=""></div>
		<script type="text/javascript">
			let btnTop = document.querySelector("img");
			let scrollTop = 0;
			window.onscroll = function() {
				scrollTop = document.body.scrollTop || document.documentElement.scrollTop;
				if (scrollTop > 300) {
					btnTop.style.display = "block";
				} else {
					btnTop.style.display = "none";
				}
			}
			btnTop.onclick = function() {
				let timer = setInterval(function() {
					scrollTop -= 30;
					if (scrollTop <= 30) {
						document.body.scrollTop = 0;
						document.documentElement.scrollTop = 0;
						clearInterval(timer);
						return;
					}
					document.body.scrollTop = scrollTop;
					document.documentElement.scrollTop = scrollTop;
				}, 10);
			}
		</script>
	</body>
</html>