Function defineExpose()

Components using <script setup> are closed by
default.

To explicitly expose properties in a
<script setup> component, use the defineExpose
compiler macro:

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

const a = 1
const b = ref(2)

defineExpose({
  a,
  b
})
</script>

When a parent gets an instance of this component
via template refs, the retrieved instance will be
of the shape { a: number, b: number } (refs are
automatically unwrapped just like on normal
instances).