[Vuejs]-Try to send from data to v-for in Vue but it look like missing something

I can fix by change

<div v-for="(item, index) in items"> {{index}}. {{item.name}} </div>

to

<div v-for="(item, index) in items" :key="item.id"> {{index}}. {{item.name}} </div>

and change data return to

data() {

  return {items: [
    {qty: 5, price: 25 },
    {qty: 2, price: 16 },
    {qty: 8, price: 320 },
    {qty: 3, price: 88 }
    ]};
},