1.在src创建一个router文件，在router.js文件
2.下载react-router-dom：

npm install react-router-dom --save-dev 

3.router.js

import {
  BrowserRouter as Router,
  Switch,
  Route,
} from "react-router-dom";
import React from 'react';
import Tab1 from '../views/tab/tab1.js'
import Tab2 from '../views/tab/tab2.js'
import Tab3 from '../views/tab/tab3/tab3.js'
export default class Router1Map extends React.Component{
    render(){
        return (
        <Router>
                <div>
                    <Route exact path="/" component={Tab1}></Route>
                    <Route path="/tab1"  component={Tab1} />//这里包括下面都不要配置exact，否则二级路由页面不显示不报错
                    <Route path="/tab2"  component={Tab2} />
                    <Route path="/tab3"  component={Tab3} />
                </div>
        </Router>
        
        )
    }
}  

在App.js

import React from 'react';

import RouteMap from "./routers/1router.js" 

function App() {
  return (
    <div className="App">
      <RouteMap />
    </div>
  );
}

export default App;

二级路由

在tab3.js文件配置二级路由

import React from 'react';
import {
     BrowserRouter as Router,
  Route,
  Link
} from 'react-router-dom'
import Tab4 from "./tab4/tab4.js"
export default class Tab3 extends React.Component {
    componentDidMount(){
        console.log(this.props.match)
    }
 render(){
    return (
    <div>
    <div className="left">
        <Link to={`${this.props.match.path}/tab4`}>路由4</Link>
    </div>
    <div className="right">
        <Route  path={`${this.props.match.path}/tab4`} component={Tab4}></Route>
    </div>
    </div>
    
    )
 }
   
}