const node = {
 title: '00000', 
 key: '0' ,
 level:'level1',
 open: true,
 child:[ 
   {
    title: '0-111111', 
    key: '0-0',
    level:'level2',
    open: true,
    child:[ 
      { 
       title: '0-1-1111', 
       key: '0-0-0',
       level:'level3',  
      }, 
      { 
       title: '0-1-2222', 
       key: '0-0-1',
       level:'level3',
       open: true,
       child: [
         { 
         title: '0-1-2-11111', 
         key: '0-0-1-0',
         level:'level4',
         open: true,
         child: [
           { 
           title: '0-1-2-1-111', 
           key: '0-0-1-0-0',
           level:'level5',
          }
         ]
        }
       ]
      },
      { 
       title: '0-1-33333', 
       key: '0-0-4',
       level:'level3',
      }, 
    ]
   },
   {
    title: '0-222222', 
    key: '0-2',
    level:'level2',
    open: false,
    child: [
     {
      title: '0-2-1111', 
      key: '0-2-0',
      level:'level3',
     },
     {
      title: '0-2-22222', 
      key: '0-2-1',
      level:'level3',
     },
     {
      title: '0-2-33333', 
      key: '0-2-2',
      level:'level3',
     }
    ]
   }
 ]
}

<div>
  <Tree 
    treeList = {node}
  /> 
</div>

import React, { Component } from 'react';
import classNames from 'classnames';
const history = createHistory();
import {
  BrowserRouter as Router,
  HashRouter,
  Route,
  Link,
  Switch,
  NavLink
 } from 'react-router-dom';

class Tree extends Component {

  constructor(props){
    super(props)
    this.treeItemCroup  = this.treeItemCroup.bind(this);
    this.handleClick   = this.handleClick.bind(this);

    this.state ={
      openList : false
    }
  }

  handleClick(e) {
    // 这是点击"rotate(-90deg)" "rotate(0deg)" : "rotate(-90deg)"
    for(let item in e.target.parentNode.parentNode.childNodes){
      // 点击的时候设置当前层级的子元素素隐藏
      // 操作了DOM,我很难受
      if(item > 0){
        e.target.parentNode.parentNode.childNodes[item].style.display = e.target.parentNode.parentNode.childNodes[item].style.display === 'none' "true" className={iconChevron} onClick={this.handleClick.bind(this)}></i>
          {this.itemTitle(itemGroup)}
        </li>
        {/* 调用tree方法 */}
        {this.tree(itemGroup.child)}
      </ul>
    )
    return itemGroupItem
  }

  tree(child){
    let treeItem
    // 如果有子元素
    if(child){ 
      // 子元素是数组的形式，把所有的子元素循环出来
      treeItem = child.map((item, key) => {
        // 同理，设置样式
        let itemStyle = {
          paddingLeft: 20*parseInt(item.level.slice(5), 10)+'px'
        }
        // 同理，设置"true" className={iconChevron} onClick={this.handleClick.bind(this)}></i>
              {this.itemTitle(item)}
            </li>
            {/* 如果当前子元素还有子元素，就递归使用tree方法，把当前子元素的子元素渲染出来 */}
            {this.tree(item.child)}
          </ul>
        )
      })
    }
    return treeItem
  }

  render() {
    return (
      <div className="tree">
        { this.treeItemCroup(this.props.treeList) }
      </div>
    );
  }
}

export default Tree;