javascript - 如何获得元素的滚动高度？

Question

我想用样式溢出-y：滚动获取元素的所有滚动-y高度我有下一个代码：

    <div class="team_comments">
<div class="col span_9">
<div id="timelineBoxContainer">
<ul id="timeline" class="clearfix">
<li>
<li>
<li style="display:none;">
<li style="display:none;">
<li style="display:none;">
</ul>
</div>
</div>
</div>

    .team_comments {
    height: 310px;
    overflow-x: hidden;
    overflow-y: scroll;
}

    #timeline:before {
    background: none repeat scroll 0 0 #8E9399;
    bottom: 0;
    content: "";
    height: 99999px;
    left: 50%;
    margin-left: -1px;
    margin-top: -10px;
    position: absolute;
    top: 10px;
    width: 2px;
}
.clearfix:before, .clearfix:after {
    content: "";
    display: table;
}
.clearfix:after {
    clear: both;
}
.clearfix:before, .clearfix:after {
    content: "";
    display: table;
}
#timeline {
    list-style: none outside none;
    margin: 0 auto;
    overflow: hidden;
    padding: 0 0 40px;
    position: relative;
    width: 100%;
}

我如何在 .team_comments 获得滚动条的高度？（不是当前位置！！！）？我认为滚动条在结束时必须与滚动顶部的位置相同。谢谢