data: () => ({
currencies: [
{ title: 'рубль', rate: 1, val: 0 },
{ title: 'доллар', rate: 62.65, val: 0 },
{ title: 'евро', rate: 60.90, val: 0 },
],
}),
methods: {
onInput({ rate, val }) {
this.currencies.forEach(n => n.val = val * rate / n.rate);
},
},
<div v-for="n in currencies">
<input
v-model.number="n.val"
@input="onInput(n)"
type="number"
min="0"
>
{{ n.title }}
</div>