vue3 侦听器有哪些写法

Vue3 侦听器有下列写法：

监听单个数据变化：

watch: {
  count: {
    handler(newVal, oldVal) {
      console.log('count changed:', newVal, oldVal)
    },
    immediate: true
  }
}

监听多个数据变化：

watch: {
  count(newVal, oldVal) {
    console.log('count changed:', newVal, oldVal)
  },
  message(newVal, oldVal) {
    console.log('message changed:', newVal, oldVal)
  }
}

监听对象属性变化：

watch: {
  userInfo: {
    handler(newVal, oldVal) {
      console.log('userInfo changed:', newVal, oldVal)
    },
    deep: true
  }
}

监听嵌套对象属性变化：

watch: {
  'userInfo.name': {
    handler(newVal, oldVal) {
      console.log('userInfo.name changed:', newVal, oldVal)
    }
  }
}

监听计算属性变化：

watch: {
  fullName(newVal, oldVal) {
    console.log('fullName changed:', newVal, oldVal)
  }
}