JSFiddle - React, Tailwind, and code Playground

HTML

<script src="//unpkg.com/vue/dist/vue.js"></script>
<script src="//unpkg.com/[email protected]/lib/index.js"></script>
<div id="app">
<el-button @click="expand">展开「一级 2」节点</el-button>
<el-button @click="collapse">收起「一级 2」节点</el-button>
<el-tree :data="data" :props="defaultProps" node-key="label" ref="tree"></el-tree>
</div>

SCSS

@import url("//unpkg.com/[email protected]/lib/theme-chalk/index.css");

Babel + JSX

var Main = {
    data() {
      return {
        data: [{
          label: '一级 1',
          children: [{
            label: '二级 1-1',
            children: [{
              label: '三级 1-1-1'
            }]
          }]
        }, {
          label: '一级 2',
          children: [{
            label: '二级 2-1',
            children: [{
              label: '三级 2-1-1'
            }]
          }, {
            label: '二级 2-2',
            children: [{
              label: '三级 2-2-1'
            }]
          }]
        }, {
          label: '一级 3',
          children: [{
            label: '二级 3-1',
            children: [{
              label: '三级 3-1-1'
            }]
          }, {
            label: '二级 3-2',
            children: [{
              label: '三级 3-2-1'
            }]
          }]
        }],
        defaultProps: {
          children: 'children',
          label: 'label'
        }
      };
    },
    methods: {
      expand() {
        this.$refs.tree.store.getNode('二级 1-1').expand();
      },
      collapse() {
        this.$refs.tree.store.getNode('一级 2').collapse();
      }
    }
  };
var Ctor = Vue.extend(Main)
new Ctor().$mount('#app')