props.js

import PropTypes from 'prop-types'

Widget.propTypes = { 
  headerText: PropTypes.string.isRequired,
  widgetCount: PropTypes.number.isRequired,
  isFetchingData: PropTypes.bool.isRequired,
  handlerFunction: PropTypes.func.isRequired,
  createdAt: PropTypes.instanceOf(Date).isRequired,
  optionalText: PropTypes.string
}