<link href="//maxcdn.bootstrapcdn.com/bootstrap/4.1.1/css/bootstrap.min.css" rel="stylesheet" id="bootstrap-css">
<script src="//maxcdn.bootstrapcdn.com/bootstrap/4.1.1/js/bootstrap.min.js"></script>
<script src="//code.jquery.com/jquery-1.11.1.min.js"></script>
<link href="https://cdnjs.cloudflare.com/ajax/libs/select2/4.0.4/css/select2.min.css" rel="stylesheet" />
<script src="https://cdnjs.cloudflare.com/ajax/libs/select2/4.0.4/js/select2.min.js"></script>
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/font-awesome/4.7.0/css/font-awesome.min.css">
<div class=" col-md-4 offset-md-4">
<select class="js-example-matcher-start form-control select2 js-select2" multiple="multiple">
<option value="O1" data-badge=""> O ption1</option>
<option value="O2" data-badge=""> O ption2</option>
<option value="O3" data-badge=""> O ption3</option>
<option value="O4" data-badge=""> O ption4</option>
<option value="O5" data-badge=""> O ption5</option>
<option value="O6" data-badge=""> O ption6</option>
<option value="O7" data-badge=""> O ption7</option>
<option value="O8" data-badge=""> O ption8</option>
<option value="O9" data-badge=""> O ption9</option>
<option value="O10" data-badge=""> O ption10</option>
<option value="O11" data-badge=""> O ption11</option>
<option value="O12" data-badge=""> O ption12</option>
<option value="O13" data-badge=""> O ption13</option>
</select>
</div>
<script>
$(".js-select2").select2({
closeOnSelect : false,
placeholder : "Placeholder",
allowHtml: true,
allowClear: true,
tags: true
});