js自定义滚动条代码

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
<style>
    html, body {
        height: 100%;
        margin: 0;
    }
    #container {
        position: absolute;
        top: 50px;
        left: 100px;
        height: 400px;
        width: 150px;
        background-color: aliceblue;
        padding: 2rem;
        box-sizing: border-box;
        /*必须属性，否则给scrollTop赋值无效*/
        overflow-y: hidden;
        position: relative;
        padding-right: 30px;
    }
    .scrollbar {
        height: 50px;
        width: 10px;
        border-radius: 20px;
        background: #ccc;
        position: absolute;
        right: 0;
    }
</style>
    <script>
    window.onload = function () {
        var scrollbar = document.querySelector('.scrollbar');
        var container = scrollbar.parentNode;
        container.scrollbar = scrollbar;
        container.ratio =
            (container.scrollHeight - container.offsetHeight) / (container.offsetHeight - scrollbar.offsetHeight);
        container.addEventListener('mousewheel', function(e) {
            this.scrollTop += e.deltaY;
            this.scrollbar.style.top = (this.scrollTop + this.scrollTop / this.ratio) + 'px';
        });
        container.addEventListener('mousedown', function (e) {
            if (e.target === this.scrollbar) {
                this.prevY = e.pageY;
            }
        });
        container.addEventListener('mouseup', function (e) {
            this.prevY = null;
        });
        container.addEventListener('mousemove', function (e) {
            if (this.prevY) {
                this.scrollTop += (e.pageY - this.prevY) * this.ratio;
                this.scrollbar.style.top = (this.scrollTop + this.scrollTop / this.ratio) + 'px';
                this.prevY = e.pageY;
            }
            e.preventDefault();
        });
    }
    </script>
</head>
<body>
    <div id="container">
        <div class="scrollbar"></div>
        <p>fefe</p>
        <p>fefe</p>
        <p>fefe</p>
        <p>fefe</p>
        <p>fefe</p>
        <p>fefe</p>
        <p>fefe</p>
        <p>fefe</p>
        <p>fefe</p>
        <p>fefe</p>
        <p>fefe</p>
        <p>fefe</p>
        <p>fefe</p>
        <p>fefe</p>
        <p>fefe</p>
        <p>fefe</p>
        <p>fefe</p>
        <p>fefe</p>
        <p>fefe</p>
        <p>fefe</p>
        <p>fefe</p>
    </div>
</body>
</html>
zhanghe-V
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js自定义滚动条代码

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