example3.jsx

const Note = props => <div>{props.note}</div>;

const SimpleNote = props => (
  <div
    style={{ color: props.selectedNoteIndex === props.index ? 'red' : 'blue' }}
  >
    <Note note={props.note} />
  </div>
);

notes.map((note, index) => (
  <SimpleNote note={note} index={index} selectedNoteIndex={selectedNoteIndex} />
));