我希望在边栏长于内容时滚动边栏.所以我用纯CSS解决了它:
我的新HTML代码:

as I told above, I wanted sidebar to be scrolled when the sidebar is longer than content. so I solved it by pure CSS:
my new HTML code:

<section class="container">
    <div class="sidebar">
        <div class="sidebardiv">
            <ul>
                <li><li>
                <li><li>
                <li><li>
                <li><li>
                <li><li>
            </ul>
        </div>
    </div>
    <div class="content"></div>
</section>

我的新CSS代码:

.container {
    display: flex;
}
.sidebar , .content {
    flex: 1 0 auto;
}
.sidebardiv {
    position: absolute;
    top: 0;
    right: 0;
    height: 100%;
    overflow: auto;
    padding: 0 8px 0 8px;
}