title: How to connect my app users with their facebook id's?
body: <p>In my app I need to find a way to connect users with their facebook ids (or something, that will identify them later). Will try to explain:</p>
  
  <ol>
  <li>As a user,I'm create an event, and mark participants by enter their names.</li>
  <li>Some of participants are already sign up in my app, some of them not.</li>
  <li>To identify participant (no matter, registered or not),I have planned to use their facebook ids. Currently,I want add links to their profiles under names.</li>
  </ol>
  
  <p>So, is there a way to get facebook id of user, by his profile link (<a href="https://facebook.com/zuck" rel="nofollow noreferrer">https://facebook.com/zuck</a>)? Or any other way to identify user via facebook, no matter registered he in app or not.</p>
  
  <p><strong>UPDATE</strong> Looks like there are no way to use facebook IDs for this task. Maybe there are another identifier to uniquely link account with facebook?</p>