Alt

Generalization over Option, Either, Result and others for the practical use in JavaScript apps.

function View () {
  const [ state, _ ] = useSomeState()

  useEffect(() => {
    state.tap_of('ERROR', error => console.error(error))
  }, [ state ])

  return <div>
  {
    state
    .map(data => <Component data={ data } />)
    .settle_of('PROGRESS', () => <Loading />)
    .settle_of('ERROR', error => <div className='error'>Error: { error.message }</div>)
    .extract()
  }
  </div>
}

extract takes OK value out of the Alt. It is exhaustive. If Alt is not settled to OK only it will return unknown type in static time and throw in run time.

StreetStrider/alt

Alt

license