...
export default class App extends Component {
  render() {
    return (
      <Router>
        <Route path="/" component={IndexPage}/>
      </Router>
    )
  }
}

...
export default class IndexPage extends Component {
  componentDidMount() {
    this.updateTitle(this.props);
  }

  componentWillUpdate(nextProps) {
    this.updateTitle(nextProps);
  }

  updateTitle = (props) => {
    routes.forEach(route => {
        if (route.path === props.location.pathname) {
          document.title = route.title;
        }
    })
  }
  render() {
    return (
      <div className="index-page">
        <Switch>
          ...
          项目一级路由
          ...
        </Switch>
      </div>
    )
  }
}