Bootstrap Modal Base

HTML

<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.2/css/bootstrap.min.css">
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.2/js/bootstrap.min.js"></script>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.2/js/bootstrap.min.js"></script>


<div class="page-container">
    <div class="container">
        <br />
        <button type="button" class="btn launchConfirm">Open modal</button>
    </div>
</div>
<div class="modal fade" id="confirm">
    <div class="modal-dialog">
        <div class="modal-content">
            <div class="modal-body" id="confirm2">
            <button type="button" class="close" data-dismiss="modal" aria-label="Close"><span aria-hidden="true">&times;</span>
                </button>
                 <h4 class="modal-title">Modal title</h4>
                 <div id="getFixed" style="background-color:red">This div should be fixed<br>and should not scroll away.</div>
                <p>One fine body&hellip;</p>
                <p>One fine body&hellip;</p>
                <p>One fine body&hellip;</p>
                <p>One fine body&hellip;</p>
                <p>One fine body&hellip;</p>
                <p>One fine body&hellip;</p>
                <p>One fine body&hellip;</p>
                <p>One fine body&hellip;</p>
                <p>One fine body&hellip;</p>
                <p>One fine body&hellip;</p>
                <p>One fine body&hellip;</p>
                <p>One fine body&hellip;</p>
                <p>One fine body&hellip;</p>
                <p>One fine body&hellip;</p>
                <p>One fine body&hellip;</p>
                <p>One fine body&hellip;</p>
                <p>One fine body&hellip;</p>
                <p>One fine body&hellip;</p>
                <p>One fine body&hellip;</p>
                <p>One fine body&hellip;</p>
                <p>One fine body&hellip;</p>
               ...

CSS

@import url( 'https://maxcdn.bootstrapcdn.com/bootstrap/3.3.2/css/bootstrap.min.css' );
.modal-open .modal {
   //overflow: hidden;
 }
 .modal-body {
   height: calc(100vh - 126px);
   overflow-y: scroll;
 }
 
 #getFixed {
   position: relative;
   left: 10px;
   width: 600px;
 }

JavaScript

$('.launchConfirm').on('click', function (e) {
    $('#confirm').modal({
        show: true
    });
});

jQuery(function($) {
  function fixDiv() {
    var $cache = $('#getFixed');
    if ($('.modal-body').scrollTop() > 50)
    {
    $cache.css({
        'position': 'fixed',
        'top': '0px',
        'left': '25px',
        'width': '600px'
      });
    }
    else
      $cache.css({
        'position': 'relative',
        'top': 'auto',
        'left': '10px'
      });
  }
  $('.modal-body').scroll(fixDiv);
  fixDiv();
});