Increment / Decrement coffeescript

gistfile1.coffee

window.ChangeQuantity ||= {}

ChangeQuantity.load = ()->
  $("input.change-quantity").click((evnt)->
    evnt.preventDefault()

    quantityField = $(this).parent().find('input.quantity')

    currVal       = parseInt(quantityField.val())

    if $(this).val() == '+'
      quantityField.val(currVal+=1)
    else
      if currVal > 0
        quantityField.val(currVal-=1)
  )

Here's the html:

<div class="select-quantity">
  <input class="change-quantity less" type="button" value="-">
  <div class="input string optional order_quantity">
    <label class="string optional control-label" for="order_quantity">Quantity</label>
    <input class="string optional qty quantity" id="order_quantity" name="order[quantity]" size="50" type="text" value="0">
  </div>
  <input class="change-quantity more" type="button" value="+">
</div>