CoffeeScript

HTML

<script src="https://netdna.bootstrapcdn.com/bootstrap/3.0.0/js/bootstrap.min.js"></script>
<link rel="stylesheet" href="https://netdna.bootstrapcdn.com/bootstrap/3.0.0/css/bootstrap.min.css">
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/select2/4.0.5/css/select2.min.css">
<script src="https://cdnjs.cloudflare.com/ajax/libs/select2/4.0.5/js/select2.min.js"></script>
<select id="e1" style="width:300px">
  <option value="AL" data-badge="3">Alabama</option>
  <option value="WY">Wyoming</option>
</select>

CoffeeScript

$("#e1").select2
  theme: "bootstrap"
  templateResult: (data) ->
    badge = $(data.element).data('badge')
    if badge
      return $(document.createTextNode(data.text + '\u00A0')).add($('<span class="badge pull-right">').text(badge))
    data.text