WhyAlwaysReturnFalse

HTML

<div id='cnt' style="text-align: center; height: 50px; background-color: yellow;">1</div>
<input class="class1" style="text-align: center; width: 128px;" type="text" value="5">
<div id='btn' style="text-align: center; height: 20px; background-color: red;">Click</div>

JavaScript

$('#btn').on('click','', function(){
var vl = $('.class1').val();
var bl = parseInt(vl) || 0;
  $('#cnt').html(bl.toString());
});