title: How can I prevent the unmount in React Components?
body: <p>I'm trying to implement a feature in my app where when the user tries to navigate away from an un-submitted form, they're given an confirm that asks them if they're sure they want to leave before saving their changes.</p>
  
  <p>The <strong>componentWillUnmount</strong> method seems like perfect candidate for this because it will fire for all the various ways that a user may abandon the form (changes a parent component state that causes it to disappear, navigates to a different route, etc...). However... I have no way to prevent the unmount when the confirm returns false.</p>
  
  <p>Any suggestions on how I can go about implementing this?</p>