code: function() {
          // Compute the amount of play left to go
          t.playLeft = t.playEnd - Date.now();
  
          // Done playing
          if (t.playLeft <= 0) {
            clearInterval(t.timer);
            t.next();
          }
  
          // Set the progress bar width
          t.setProgress();
        }
docs: Run at each animation interval