Confirming Navigation with React Router without Mixin for es6 Classes

With React Router is there a way to use confirm leaving a route without using a mixin? We are using es6 Classes and can't use a mixin.

This is what I am trying to accomplish: https://github.com/rackt/react-router/blob/latest/docs/guides/advanced/ConfirmingNavigation.md

You will need to use History module and then make use of listenBefore():

history.listenBefore(function (location) {
  if (input.value !== '') {
    return 'Are you sure you want to leave this page?'
  }
})

Check the Confirming Navigation docs.