scoll.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <meta name="viewport" content="width=device-width,initial-scale=1.0,maximum-scale=1.0,minimum-scale=1.0,user-scalable=no" />
    <script src="https://cdn.bootcss.com/jquery/3.3.1/jquery.min.js"></script>
    <style>
        body{
            height:3000px;
        }
        #showFont{
            font-size: 200px;
            text-align: center;
            position: fixed;
            top:0;
            left: 0;
            bottom: 0;
            right: 0;
            background-color: #66afe9;
        }
        .innerFont{
            position: absolute;
            top: 50%;
            left:50%;
            margin-left: -100px;
            margin-top: -120px;
        }
    </style>
</head>
<body>
    <div id="showFont">
        <div class="innerFont">你</div>
    </div>
<script>
    $(document).ready(function(){//在文档加载完毕后执行

        function randomColor() {
            var color = "";
            for (var i = 0; i < 6; i++) {
                color += (Math.random() * 16 | 0).toString(16);
            }
            return "#" + color;
        }
        $(window).scroll(function(){//开始监听滚动条

//获取当前滚动条高度
            var _color1 = randomColor();
            var _color2 = randomColor();
            var topp = $(document).scrollTop();
//用于调试 弹出当前滚动条高度
            if(topp <500){
                $(".innerFont").text('你')
            }else if(topp>=500&&topp<=1000){
                $(".innerFont").text('划');
            }else if(topp>=1000&&topp<=1500){
                $(".innerFont").text('个');
            }else if(topp>=1500){
                $(".innerFont").text('屁');
            }
            $(".innerFont").css('color',_color1);
            $("#showFont").css('background-color',_color2);
        })

    })
</script>
</body>
</html>