vant/packages/badge/src/badge-group.vue

<template>
  <div class="z-badge-group">
    <slot></slot>
  </div>
</template>

<script>
export default {
  name: 'z-badge-group',
  props: {
    // 当前激活 tab 面板的 key
    activeKey: {
      type: [Number, String],
      default: 0
    }
  },
  data () {
    return {
      computedActiveKey: this.activeKey
    }
  }
};
</script>