Add TS definitions for onViewModeChange callback

Simon Egersand

2017-07-29 b8d07e854fd368d56ecf918212757b9c8d667feb

 typings/react-datetime-tests.tsx

@@ -81,6 +81,9 @@
      onBlur={
         (momentOrInputString:string) => {}
      }
      onViewModeChange={
          (viewMode:string) => {}
       }
    />;

const TEST_EVENT_HANDLERS_WITH_MOMENT: JSX.Element = <ReactDatetime