Extend your facebook authentication token.

fb.js

  function fbExtendAuthentication(accessToken){
    var extensionData = {
      grant_type: 'fb_exchange_token',
      client_id: '', //App ID
      client_secret: '', //App Secret, only secure because only admins see this page
      fb_exchange_token: accessToken,
    };
    
    $.ajax('https://graph.facebook.com/oauth/access_token', {
      data: extensionData,
      complete: function( jqXHR, status) {
        console.log("Facebook extended access response:");
        console.log(jqXHR);
        if(jqXHR.status == 200){
          console.log("data-extended-access-token" + jqXHR.responseText.split('&')[0].split('=')[1]);
          console.log("#facebook-data" + jqXHR.responseText.split('&')[0].split('=')[1]);
        } else {
          console.log("Error retrieving extended-access-token from Facebook API.");
        }
      }
    });
  }