Seems like I am doing a lot of boilerplate here for TypeScript, any suggestions on making it more concise?

untyped.js

// This is how I would traditionally do it
export const selector = 'toasts'

export const actionTypes = {
  ADD: `${selector}/ADD`,
  SHOW: `${selector}/SHOW`,
  HIDE: `${selector}/HIDE`,
}

export const reducer = (state = {}, action) => {
  switch (action.type) {
    case SHOW: {
      return {
        ...state,
        [action.id]: {
          message: action.message,
        }
      }
    }
    case HIDE: {
      const newState: State = { ...state }
      delete newState[action.id]
      return newState
    }
    default:
      return state
  }
}

export const actions = {
  add: ({ message }) => ({
    type: ADD,
    message,
  }),
  show: ({ id, message }) => ({
    type: SHOW,
    id,
    message,
  }),
  hide: ({ id }) => ({
    type: HIDE,
    id,
  }),
}

export const selectors = {
  get: ({ state }) => state[selector]
}

working.ts

export const selector = 'toasts'

// Typescript doesnt like when we auto-generate these with `${selector}/ACTION`
const ADD = `toasts/ADD`
const SHOW = `toasts/SHOW`
const HIDE = `toasts/HIDE`

export const actionTypes: any = {
  ADD,
  SHOW,
  HIDE,
}

interface State {
  [id: string]: {
    message: string,
  }
}

const initialState: State = {}

export const reducer = (state: State = initialState, action: Actions) => {
  switch (action.type) {
    case SHOW: {
      return {
        ...state,
        [action.id]: {
          message: action.message,
        }
      }
    }
    case HIDE: {
      const newState: State = { ...state }
      delete newState[action.id]
      return newState
    }
    default:
      return state
  }
}

export type Actions = ShowAction | HideAction | AddAction

export interface AddActionParams {
  message: string;
}

export type AddAction = AddActionParams & {
  type: typeof ADD,
}

export interface ShowActionParams {
  id: string;
  message: string;
}

export type ShowAction = ShowActionParams & {
  type: typeof SHOW,
}

export interface HideActionParams {
  id: string;
}

export type HideAction = HideActionParams & {
  type: typeof HIDE,
}

export const actions = {
  add: ({ message }: AddActionParams): AddAction => ({
    type: ADD,
    message,
  }),
  show: ({ id, message }: ShowActionParams): ShowAction => ({
    type: SHOW,
    id,
    message,
  }),
  hide: ({ id }: HideActionParams): HideAction => ({
    type: HIDE,
    id,
  }),
}

export const selectors = {
  get: ({ state }: any) => state[selector]
}

export const actionTypes = {
  ADD: `${selector}/ADD`,
  SHOW: `${selector}/SHOW`,
  HIDE: `${selector}/HIDE`,
}

you could use an enum instead

export enum ReduxActionType {
 add = "toasts/add",
 show = "toasts/show",
 remove = "toasts/remove",
}