immutable.example.js

const initialState = Immutable.fromJS({
  status: null,
  error: null,
  items: Immutable.List([]),
  nested: {
    test: 'a',
    groups: {
      users: []
    }
  }
})

const updateState = initialState
  .set('status', 'active')
  .set('error', false)
  .update('items', (list: any) => list.push('a', 'b', 'c'))
  .update('items', (list: any) => list.delete(list.keyOf('b')))
  .setIn(['nested', 'groups', 'users'], Immutable.List([1, 2, 3]))