#vue3
[[Composition APIでcomputed]]した値を[[Composition APIでwatch]]したい場合は`<computed_value>.value`を使う。
```ts
import {
defineComponent,
watch,
computed,
} from "@vue/composition-api";
export default defineComponent({
setup() {
const computedValue = computed(() => ...)
watch(
// computedValue ではダメ
() => computedValue.value,
(new, old) => console.log(`新しい値は ${new}`)
);
}
})
```