code: function handleFocusToOpenEvent( event ) {
  
          // Stop the event from propagating to the doc.
          event.stopPropagation()
  
          // If it’s a focus event, add the “focused” class to the root.
          if ( event.type == 'focus' ) {
              P.$root.addClass( CLASSES.focused )
          }
  
          // And then finally open the picker.
          P.open()
      }
docs: Separated for IE