core/packages/vue/examples/composition/tree.html

<script src="../../dist/vue.global.js"></script>

<!-- item template -->
<script type="text/x-template" id="item-template">
  <li>
    <div
      :class="{bold: isFolder}"
      @click="toggle"
      @dblclick="changeType">
      {{model.name}}
      <span v-if="isFolder">[{{open ? '-' : '+'}}]</span>
    </div>
    <ul v-if="isFolder" v-show="open">
      <tree-item
        class="item"
        v-for="model in model.children"
        :model="model">
      </tree-item>
      <li class="add" @click="addChild">+</li>
    </ul>
  </li>
</script>
<!-- item script -->
<script>
const { reactive, computed, toRefs } = Vue

const TreeItem = {
  name: 'TreeItem', // necessary for self-reference
  template: '#item-template',
  props: {
    model: Object
  },
  setup(props) {
    const state = reactive({
      open: false,
      isFolder: computed(() => {
        return props.model.children && props.model.children.length
      })
    })

    function toggle() {
      state.open = !state.open
    }

    function changeType() {
      if (!state.isFolder) {
        props.model.children = []
        addChild()
        state.open = true
      }
    }

    function addChild() {
      props.model.children.push({ name: 'new stuff' })
    }

    return {
      ...toRefs(state),
      toggle,
      changeType,
      addChild
    }
  }
}
</script>

<p>(You can double click on an item to turn it into a folder.)</p>

<!-- the app root element -->
<ul id="demo">
  <tree-item class="item" :model="treeData"></tree-item>
</ul>

<script>
const treeData = {
  name: 'My Tree',
  children: [
    { name: 'hello' },
    { name: 'wat' },
    {
      name: 'child folder',
      children: [
        {
          name: 'child folder',
          children: [
            { name: 'hello' },
            { name: 'wat' }
          ]
        },
        { name: 'hello' },
        { name: 'wat' },
        {
          name: 'child folder',
          children: [
            { name: 'hello' },
            { name: 'wat' }
          ]
        }
      ]
    }
  ]
}

Vue.createApp({
  components: {
    TreeItem
  },
  data: () => ({
    treeData
  })
}).mount('#demo')
</script>

<style>
  body {
    font-family: Menlo, Consolas, monospace;
    color: #444;
  }
  .item {
    cursor: pointer;
  }
  .bold {
    font-weight: bold;
  }
  ul {
    padding-left: 1em;
    line-height: 1.5em;
    list-style-type: dot;
  }
</style>