Discussion on: JavaScript error handling pattern tip

function match(value, patterns) {
  const { type = null } = value || {};
  const _match = patterns[type];

  if(typeof _match == 'function') {
    return _match(value.data);
  } else if (typeof patterns._ == 'function') {
    return patterns._();
  }
  else {
    return;
  }
}

function Union(types) {
  return types.reduce((target, type) => {
    target[type] = (data) => ({
      type,
      data,
      match: patterns => match({type, data}, patterns)
    });
    return target;
  }, {});
}

const Result = Union(['Ok', 'Err']);
const something = Result.Ok({ stuff: 'good stuff' });
const maybe = Result.Err('this is still data');

something.match({
  Ok: ({stuff}) => `the ${stuff}`,
  Err: (msg) => msg,
  _: () => 'What?'
});

// the good stuff