JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<link rel="stylesheet" href="https://netdna.bootstrapcdn.com/bootstrap/3.2.0/css/bootstrap.min.css">
<script src="https://rawgit.com/stefansundin/bootstrap/compiled/dist/js/bootstrap.min.js"></script>
<div class="text-center">
  <h1>Test Modal Scrollbar Bug</h1>
  <p><b>This is the fixed version!</b></p>
  <p>First, open modal when scrollbar is present. Close modal.</p>
  <p>Then, resize window so scrollbar disappears.</p>
  <p>Open modal again, this content should not shift.</p>

  <!-- Button trigger modal -->
  <button class="btn btn-primary btn-lg" data-toggle="modal" data-target="#myModal">
    Open modal
  </button>

  <p>Lots of content</p>
  <p>Lots of content</p>
  <p>Lots of content</p>
  <p>Lots of content</p>
  <p>Lots of content</p>
  <p>Lots of content</p>
  <p>Lots of content</p>
  <p>Lots of content</p>
  <p>Lots of content</p>
  <p>Lots of content</p>
  <p>Lots of content</p>
  <p>Lots of content</p>
  <p>Lots of content</p>
</div>

<!-- Modal -->
<div class="modal fade" id="myModal" tabindex="-1" role="dialog" aria-labelledby="myModalLabel" aria-hidden="true">
  <div class="modal-dialog">
    <div class="modal-content">
      <div class="modal-header">
        <button type="button" class="close" data-dismiss="modal"><span aria-hidden="true">&times;</span><span class="sr-only">Close</span></button>
        <h4 class="modal-title" id="myModalLabel">Modal title</h4>
      </div>
      <div class="modal-body">
        ...
      </div>
      <div class="modal-footer">
        <button type="button" class="btn btn-primary" data-dismiss="modal">Close</button>
      </div>
    </div>
  </div>
</div>