Increment variable by more than 1?

Question

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.

Answer 1

Use a compound assignment operator:

v += 4;

Answer 2

Use variable += value; to increment by more than one:

v += 4;

It works with some other operators too:

v -= 4;
v *= 4;
v /= 4;
v %= 4;
v <<= 1;
v >>= 4;

Answer 3

To increase v by n: v += n