I have the following object with orders of a restaurant. 

```
   var obj = {
      orders: [
        null,
        {
          date: "2018-07-09 10:07:18",
          orderVerified : true,
          item: [
            {
              name: "apple juice",
              price: 3.9,
              quantity: 1,
              isDrink: true 
            },
            {
              name: "Hawaii pizza",
              price: 7,
              quantity: 2,
              isDrink: false
            }
          ]
        },
        {
          date: "2018-07-09 10:07:30",
          orderVerified : false,
          item: [
            {
              name: "Warmer Topfenstrudel",
              price: 3.9,
              quantity: 1,
              isDrink: false
            }
          ]
        },
        {
          date: "2018-07-09 15:07:18",
          orderVerified : true,
          item: [
            {
              name: "Coca Cola 2 l",
              price: 12.9,
              quantity: 3,
              isDrink:true
            }
          ]
        },
        {
          date: "2018-06-13 10:07:18",
          orderVerified : true,
          item: [
            {
              name: "Wiener Schnitzel vom Schwein",
              price: 9.9,
              quantity: 2,
              isDrink: false
            }
          ]
        }
      ]
    };

```

I want to summing up the item's prices \* items quantities if the value of isDrink is true.
I've tried to use this function, which get the total of all items. but I can check check wether isDrink is true or false, but how could I summing up the drinks prices \* quantities?

```
 fullTotal: function(arr) {
    if (arr!=''){
    return arr.reduce((sum, order) => {
      return sum + order.item.reduce((itemSum, item) => (
        itemSum + (item.price * item.quantity)
      ), 0)
    },0)}
    else {return 0}
  },

```

Please give me some suggestion with this. Thank you!