choonkending

const transformCage = () => { /* ... */ };
const handleError = e => "Invalid or Corrupted User Data";
const handleSuccess = data => "Success";

const doSomethingWithUserData = () => 
  getUserFromLocalStorage('nickCage')
    .map(transformCage)
    .fold(handleError, handleSuccess);

choonkending

const getUserFromLocalStorage = keyName => {
  const str = localStorage.getItem(keyName);
  try {
    return Right(JSON.parse(str));
  } catch (e) {
    return Left("Invalid or Corrupted User Data");
  }
};

choonkending

const getUserFromLocalStorage = keyName => {
  const str = localStorage.getItem(keyName);
  try {
    return JSON.parse(str);
  } catch (e) {
    return "Invalid or Corrupted User Data";
  }
};

choonkending

const doSomethingWithUserData = () => {
  const cage = getUserFromLocalStorage('cage');
  // do wonderful things
};

choonkending

const getUserFromLocalStorage = keyName => {
  const str = localStorage.getItem(keyName);
  return JSON.parse(str);
};

choonkending

const Left = x => ({
  map: f => Left(x),
  fold: (ifLeft, ifRight) => ifLeft(x)
});

const Right = x => ({
  map: f => Right(f(x)),
  fold: (ifLeft, ifRight) => ifRight(x)
});

choonkending

const getBedrooms = data =>
    Option(data.listing)
        .flatMap(listing => Option(listing.features))
        .flatMap(features => Option(features.bedrooms))
        .map(bedrooms => bedrooms.value)
        .fold(() => 0, v => v);
   

choonkending

const Option = x => (x === undefined || x === null) ? None : Some(x);

const Some = x => ({
  map: f => Some(f(x)),
  flatMap: f => f(x),
  fold: (ifEmpty, f) => f(x)
});

const None = {
  map: f => None,

choonkending

const ComponentThatWrapsFeatures = ({ data }) => {
  const features = getFeatures(data);
  return features && <Features {...features} />
};

choonkending

const Features = ({ bedrooms, bathrooms }) => (
  <div>
    <span>Beds: </span><span>{ bedrooms }</span>
    <span>Baths: </span><span>{ bathrooms }</span>
  </div>
);