React Router - how to constrain params in route matching? : <p>I don't really get how to constrain params with, for example a regex.<br>
How to differentiate these two routes?</p>

<pre><code>  &lt;Router&gt;
    &lt;Route path="/:alpha_index" component={Child1} /&gt;
    &lt;Route path="/:numeric_index" component={Child2} /&gt;
  &lt;/Router&gt;
</code></pre>

<p>And prevent "/123" from firing the first route?</p>
