排错

如何获得上一次路径？

<Route component={App}>
  {/* ... 其它 route */}
</Route>
const App = React.createClass({
  getInitialState() {
    return { showBackButton: false }
  },
  componentWillReceiveProps(nextProps) {
    const routeChanged = nextProps.location !== this.props.location
    this.setState({ showBackButton: routeChanged })
  }
})