实例 使用 $slots 对象检查父级是否为 'topSlot' 提供了内容

<template>

  <h1>App.vue</h1>

  <p>The component has two slots, but the 'topSlot' is not used by the parent.</p>

  <slot-comp>

    <!-- <template v-slot:topSlot>Content for 'bottomSlot'</template> -->

    <template v-slot:bottomSlot>Content for 'bottomSlot'</template>

  </slot-comp>

</template>

​

<script></script>

​

<style>

  #app {

    width: 300px;

  }

</style>