The focus event is triggered either on mouse hover or when the keyboard cursor keys are used for navigation. In general, an item or element that has focus is highlighted in some way. When an item or element has focus it is the first to receive keyboard-related events.

var instance; // Type: options
instance.focus = function(e, data) { };

focus = function ( 
   e : jQuery.Event,
   data : IFocusEventArgs
) { };