JSFiddle - React, Tailwind, and code Playground

HTML

<!-- Latest compiled and minified JavaScript -->
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js" integrity="sha384-Tc5IQib027qvyjSMfHjOMaLkfuWVxZxUPnCJA7l2mCWNIpG9mGCD8wGNIcPD7Txa" crossorigin="anonymous"></script>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>


<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

<input name="distancia" type="text" id="txtDistancia" value="7,5 km">
<p></p>
<input type="button" value="Testar" id="testar" class="btn btn-success" />
<p></p>
<div id="valorkm"></div>

CSS

#valorkm {
	size:16px;
}

JavaScript

$("#testar").click(function() {

  let valor = $('#txtDistancia').val().match(/\d+/g);
  $('#valorkm').html(valor);
});