title: How do you scroll this on Bilibili.com with JavaScript?
body: <p>I tried to scroll an element that includes comments of a video on Bilibili.com. </p>
  
  <p>Example URL here: <a href="https://www.bilibili.com/video//?spm_id_from=333.334.chief_recommend.16" rel="nofollow noreferrer">https://www.bilibili.com/video//?spm_id_from=333.334.chief_recommend.16</a></p>
  
  <p>The comment area is in the right of page. </p>
  
  <p>I tried to run following four JavaScript expressions.</p>
  
  <pre><code>document.querySelector('#mCSB_2_scrollbar_vertical &gt; div &gt; div.mCSB_draggerRail').scrollBy(0, 100)
  document.querySelector('#mCSB_2_scrollbar_vertical &gt; div &gt; div.mCSB_draggerRail').scrollTop += 100;
  document.querySelector('li[dmno="1"]').scrollBy(0, 100)
  document.querySelector('li[dmno="1"]').scrollTop += 100;
  </code></pre>
  
  <p>But none of them work.</p>
  
  <p>How would you do it?</p>
  
  <h2>Edit</h2>
  
  <p>Oh, I'm sorry. I posted mistaken URL. </p>
  
  <p>Not correct: : <a href="https://www.bilibili.com/video//?spm_id_from=333.334.chief_recommend.16" rel="nofollow noreferrer">https://www.bilibili.com/video//?spm_id_from=333.334.chief_recommend.16</a></p>
  
  <p>corrent: <a href="https://www.bilibili.com/video/av31026102/?spm_id_from=333.334.chief_recommend.16" rel="nofollow noreferrer">https://www.bilibili.com/video/av31026102/?spm_id_from=333.334.chief_recommend.16</a></p>
  
  <p>@tadman No error occured. Each JavaScript output just "undefined" or "100" like following.</p>
  
  <pre><code>document.querySelector('#mCSB_2_scrollbar_vertical &gt; div &gt; div.mCSB_draggerRail').scrollBy(0, 100)
  # =&gt; undefined
  document.querySelector('#mCSB_2_scrollbar_vertical &gt; div &gt; div.mCSB_draggerRail').scrollTop += 100;
  # =&gt; 100
  document.querySelector('li[dmno="1"]').scrollBy(0, 100)
  # =&gt; undefined
  document.querySelector('li[dmno="1"]').scrollTop += 100;
  # =&gt; 100
  </code></pre>