<template>

  <Input v-model="msg.aaa" />

  <button @click="onClick">click</button>

  {{txt}}

</template>

<script setup>

  import { ref, reactive } from 'vue'

  const msg = reactive({})

  const txt = ref("")

  const onClick = () => {

    txt.value = msg.aaa

  }

</script>

​