title: Is there a browser tab identifier that I can set or use locally?
body: <p>(I am developing a Node.js/Express web application.)</p>
  
  <p>Is there a way to identify a tab and have its identifier saved locally in the browser so that the identifier is persistent across different pages of the same web site?</p>
  
  <p>Example, my web application is opened by the user in two tabs of the same browser. I would like to know that they are opened in different tabs. Even if the user in tab A presses F5 to refresh the page, I (in the client Javascript) would like to know that the page is still in tab A.</p>
  
  <p>Is there a property of <code>window</code> or another object in the DOM that identifies the browser tab?</p>