<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
<script src="./js/jquery.min.js"></script>
<style>
.back {
position: fixed;
width: 50px;
height: 50px;
background-color: pink;
right: 30px;
bottom: 100px;
display: none;
}
.container {
width: 900px;
height: 500px;
background-color: skyblue;
margin: 400px auto;
}
</style>
</head>
<body>
<div class="back">返回顶部
</div>
<div class="container"></div>
<script>
$(function() {
//被卷起了多少
var boxTop = $(".container").offset().top;
$(window).scroll(function() {
// console.log(11);
//$(document).scrollTop();
console.log($(document).scrollTop());
if ($(document).scrollTop() > boxTop) {
$(".back").fadeIn();
} else {
$(".back").fadeOut();
}
})
})
</script>
</body>
</html>
运行结果
