How to calculate price while using array in Ionic framework

I have a little problem while develop an app in ionic : calculating price while using array.

You can take a look at this codepen : http://codepen.io/harked/pen/gpvdNK

There is initial price worth: $10.00 in the total price. When user click on (+) button to add item, i.e : LAKSA (price $4.5), the price will be updated to : $14.50 (and the button will be change to (-) minus with red background). and then When user add BURGER (price $2.5), the price will be updated to : $17.00.

then, when user click on the LAKSA again, the price will be decrease to $12.5. and so on .. that's happen with the all item.

I've found another code here : [http://codepen.io/harked/pen/KpQrMW][1] which is looks like my case. But i get stuck on how to implement this with my case.

Anyone have a clue/advice? It would be greatly appreciated.

Just bind the initial price to the $scope directly and update the value in your onClickAdd() function. 

<div class="item item-divider">Restaurant 1<span class="item-note">$ {{initialPrice}}</span></div>

In your controller:

$scope.initialPrice = 10;

$scope.onClickAdd = function(item){
    if(!item.added)
      $scope.initialPrice+=item.price
    else
      $scope.initialPrice-=item.price

    item.added = !item.added;
};

Codepen here.