reactjs - React Router - how to constrain params in route matching?

Question

I don't really get how to constrain params with, for example a regex.
How to differentiate these two routes?

  <Router>
    <Route path="/:alpha_index" component={Child1} />
    <Route path="/:numeric_index" component={Child2} />
  </Router>

And prevent "/123" from firing the first route?

question from:https://stackoverflow.com/questions/37269736/react-router-how-to-constrain-params-in-route-matching

Answer 1

React-router v4 now allows you to use regexes to match params -- https://reacttraining.com/react-router/web/api/Route/path-string

const NumberRoute = () => <div>Number Route</div>;
const StringRoute = () => <div>String Route</div>;

<Router>
    <Switch>
        <Route exact path="/foo/:id(\d+)" component={NumberRoute}/>
        <Route exact path="/foo/:path(\w+)" component={StringRoute}/>
    </Switch>
</Router>

More info: https://github.com/pillarjs/path-to-regexp/tree/v1.7.0#custom-match-parameters