Here's my script :

function itemQuantityHandler(operation, cart_item) {

  var v = cart_item.quantity;



  //add one

  if (operation === 'add' && v < settings.productBuyLimit) {

    v++;

  }



  //substract one

  if (operation === 'subtract' && v > 1) {

    v--;

  }



  //update quantity in shopping cart

  $('.item-quantity').text(v);



  //save new quantity to cart

  cart_item.quantity = v;

}

What I need is to increase v (cart_item.quantity) by more than one. Here, it's using v++, but it's only increasing by 1. How can I change this to make it increase by 4 every time I click on the plus icon?

I tried

v++ +4

But it's not working.