Specify custom behavior on focus event.
Note: As the focus event is executed synchronously when calling input.focus()
AngularJS executes the expression using scope.$evalAsync if the event is fired
during an $apply to ensure a consistent state.
<window, input, select, textarea, a
  ng-focus="">
...
</window, input, select, textarea, a>| Param | Type | Details | 
|---|---|---|
| ngFocus | expression | Expression to evaluate upon
focus. (Event object is available as  | 
See ngClick