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回到顶部效果

回到顶部效果:

可以中途暂停,达到一屏幕才出现totop按钮,不到一屏按钮消失。

<!DOCTYPE html><html lang="en"><head>	<meta charset="UTF-8">	<title>回到顶部效果</title>	<style>		body {			height: 10000px;		}		p {			position: fixed;			right: 20px;			bottom: 20px;			width: 50px;			height: 50px;			background: rgba(102,102,102,0.3);			font-size: 18px;			line-height: 50px;			text-align: center;			color: #333;			cursor: pointer;			display: none;		}		p:hover {			background: rgba(102,102,102,1);			color: #fff;		}	</style></head><body>	<p id="totop">Totop</p>	<script>		window.onload = function () {			var totop = document.getElementById(‘totop‘);			var clientHeight = document.documentElement.clientHeight;			console.log(clientHeight);			var timer = null;			var isTop = true;			window.onscroll = function () {				var t = document.documentElement.scrollTop || document.body.scrollTop;				console.log(t);				if (t >= clientHeight) {					totop.style.display =‘block‘;				}else if(t < clientHeight) {					totop.style.display =‘none‘;				}				if(!isTop) {					clearInterval(timer);				}				isTop = false;			}			totop.onclick = function () {				clearInterval(timer);				timer = setInterval(function () {					//获取滚动条距离顶部的距离					var t = document.documentElement.scrollTop || document.body.scrollTop;					var speed = Math.floor(-t / 30);					document.documentElement.scrollTop = document.body.scrollTop = t + speed;					console.log(t - speed);					isTop = true;					if (t == 0) {						clearInterval(timer);					}				}, 30);			}		}	</script></body></html>

  

回到顶部效果