I made a little script that gets a value from a selectbox. The selectbox value can be changed with plus and minus arrows. 

I'm trying to increase that value with 4 or 6 but that gives me a wrong value over and over again. 

So in short: I want the value inside increased by 4 or 6 or decreased by 4 or 6. 

HTML

```
<div class="quantity">
  <input type="text" name="quantity" value="{{ product.quantity }}" />
    <div class="change">
      <a href="javascript:;" onclick="updateQuantity('up');" class="up">+</a>
      <a href="javascript:;" onclick="updateQuantity('down');" class="down">-</a>
    </div>
</div>

```

JQUERY

```
 function updateQuantity(way){

  if(6 == 4){ //6 is a Twig tag and works. This is the only way to test if it's 4 or 6
    var qty = '4';
  }else {
    var qty = '6';
  }

    var quantity = parseInt($('.quantity input').val());

    if (way == 'up'){
        if (quantity < 100){
            quantity+qty; // gives me something like 444 or 666
        } else {
            quantity = 100;
        }
    } else {
        if (quantity > 6){
            quantity-qty; // actually works
        } else {
            quantity = 6;
        }
    }

    $('.quantity input').val(quantity);
}

```

Does anyone know what I'm doing wrong? I really can't see it anymore