[react-router.v4] Uncaught TypeError: Cannot read property 'location' of undefined

1. 选择 react-router 和 react-router-dom
   只需引用一个，两者之处就是dom多了 这样的 DOM 类组件

2. 报错 Uncaught TypeError: Cannot read property 'location' of undefined

impt 引用时写

import React from "react";
import { render } from "react-dom";

import { BrowserRouter as Router, Route, Link } from "react-router-dom";

const Home = () => {
  return (
    

      
test home
    
  );
};

const about = () => {
  return (
    

      
test about
    
  );
};

const topics = () => {
  return (
    

      
test topics
    
  );
};

render(
  
    

      

        

          首页
        
        

          关于
        
        

          主题列表
        
      

      
      
      
    
  ,

  document.getElementById("root")
);