<!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>
        .recommend {
            height: 1000px;
            background-color: red;
        }
        
        .fixedtool {
            width: 100px;
            height: 101px;
            background-color: pink;
        }
    </style>
</head>
 
<body>
    <div class="recommend">1</div>
    <div class="fixedtool">2</div>
    <script>
        $(function() {
            var toolTop = $(".recommend").offset().top;
            $(window).scroll(function() {
                if ($(document).scrollTop() >= toolTop) {
                    $(".fixedtool").fadeIn();
                } else {
                    $(".fixedtool").fadeOut();
                }
            })
        })
    </script>
</body>
 
</html>

jquery-品优购电梯导航-71_jquery