JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css">
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.1.1/jquery.min.js"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js"></script>

<button type="button" class="btn btn-primary btn-lg" data-toggle="modal" data-target="#registerModal">Register</button> 

<div>
   <div class="modal fade" id="registerModal" tabindex="-1" role="dialog" aria-labelledby="myModalLabel">
      <div class="modal-dialog" role="document">
        <div class="modal-content">
          <div class="modal-header">
            <button type="button" class="close" data-dismiss="modal" aria-label="Close"><span aria-hidden="true">&times;</span></button>
            <h3 class="modal-title" id="myModalLabel">Fill this stuff</h3>
          </div>
          <div class="modal-body">

            <form>
              <div class="form-group">
                <label for="name">Name:</label>
                <input type="text" class="form-control" id="name" name="name" >
              </div>

              <div class="form-group">
                <label for="name">number:</label>
                <div class="input-group">
                  <div class="input-group-btn">
                    <button type="button" class="btn btn-default dropdown-toggle" data-toggle="dropdown" aria-haspopup="true" aria-expanded="true">number <span class="caret"></span></button>
                    <ul class="dropdown-menu">
                      <li><a href="#">1</a></li>
                      <li><a href="#">2</a></li>
                      <li><a href="#">3</a></li>
                      <li><a href="#">4</a></li>
                      <li><a href="#">5</a></li>

                    </ul>
                  </div><!-- /btn-group -->
                  <input type="text" class="form-control" placeholder="choose.."aria-label="..." id="number" name="number" >
                </div><!--...