<div class="container mt-5">
                     <div class="row">
                        <div class="col-sm-4"></div>
                        <div class="col-sm-4 col-sm-offset-4">
                            <div class="input-group mb-3">
                                <div class="input-group-prepend">
                                    <button class="btn btn-dark btn-sm" id="minus-btn"><i class="fa fa-minus"></i></button>
                                </div>
                                <input type="number" id="qty_input" class="form-control form-control-sm" value="1" min="1">
                                <div class="input-group-prepend">
                                    <button class="btn btn-dark btn-sm" id="plus-btn"><i class="fa fa-plus"></i></button>
                                </div>
                            </div>
                        </div>
                        <div class="col-sm-4"></div>
                    </div>
                </div>

<script>
          	$(document).ready(function(){
    $('#qty_input').prop('disabled', true);
    $('#plus-btn').click(function(){
    	$('#qty_input').val(parseInt($('#qty_input').val()) + 1 );
    	    });
        $('#minus-btn').click(function(){
    	$('#qty_input').val(parseInt($('#qty_input').val()) - 1 );
    	if ($('#qty_input').val() == 0) {
			$('#qty_input').val(1);
		}

    	    });
 });
                          </script>