Passing part of an url to another function in React - reactjs

Question

Is there a way for React to take the back of an url user entered and pass it to a function? for example: www.site.com/foobar will pass the foobar to a function.
Essencially what i'm trying to do is to run a check on foobar being in my database inside the checker function, if not there display 404 page not found.
const NotFound = () => (<h1>404.. This page is not found!</h1>)
class App extends Component {
checker : function(e){
if(foobar exists)
//load page with data
else
// {NotFound}
}
render() {
return (
<Router history={hashHistory}>
<Route path='/' component={LoginPage} />
<Route path='*' component={this.checker()} />
</Router>
)
}
}

Answer 1

To expand what I had written in my comment -
class App extends React.Component {
render() {
return (
<Router history={hashHistory}>
<Route path='/' component={LoginPage} />
<Route path='/:token' component={EmailValidation} />
</Router>
)
}
}
class EmailValidation extends React.Component {
state = { checked: false, valid: false }
componentDidMount = () => {
checkToken(this.props.params.token).then((valid) => {
this.setState({ checked: true, valid })
})
}
render() {
const { checked, valid } = this.state
return (
<div>
{ checked
? <div>{ valid ? 'valid' : 'invalid' }</div>
: <div>Checking token...</div> }
</div>
)
}
}
this would be a good use case for an HoC which conditionally renders either the component you want or a 404 page - it would remove the binding between the 404 page and the email validate component (which are only sorta-kinda related)
if you're into using libraries, recompose has a bunch of nice helpers which can accomplish something like this for you.
something else you can do is use react-router's onEnter callback/prop although, iirc, you can't directly access props from that callback.