Vue Writable computed

限制：getter 的返回值與 setter  的參數要一致。

e.g. 下例都是 string、不然 editor compiler 會叫錯

<script setup>
import { ref, computed } from 'vue'

const firstName = ref('John')
const lastName = ref('Doe')

const fullName = computed({
  // getter
  get():string {
    return firstName.value + ' ' + lastName.value
  },
  // setter
  set(newValue:string) {
    // Note: we are using destructuring assignment syntax here.
    [firstName.value, lastName.value] = newValue.split(' ')
  }
})
</script>