redux-concise

Introduction

This library was created with the intent of reducing the amount of boilerplate code needed to write Redux reducers. It is a collection of reducer creators, which are higher order functions that output a fully functional reducer. The reducer creators provided here help to create reducers for some of the most common use cases for different JavaScript data structures. This library is heavily inspired by redux-data-structures.

Installation

This library is distrubuted on npm, and has no dependencies.

npm install --save redux-concise

Data Structures

redux-concise contains reducer creators for the following data structures:

• Boolean
• Value
• Array
• Object

Example

Let's create the reducers for the todo app written in the Redux documentation with redux-concise so we can see how concise we can get our code to be.

import { 
  createValReducer, 
  createArrReducer
} from 'redux-concise'
 
const visibilityFilter = createValReducer(SHOW_ALL, {
  SET_VISIBILITY_FILTER: 'update'
})
 
const todos = createArrReducer([], {
  ADD_TODO: 'push',
  TOGGLE_TODO: 'updateIndex'
})

Let's break this down. In this example, both reducer creators are taking two arguments. The first is simply the initialState. The second argument is an object that maps action types to handler functions that return the next state. These functions are built in to the reducer creators, and are therefore referred to as default handlers.

You can either use raw strings in order to assign these handler functions to the appropriate action type, or you can import the built in HandlerTypes object from redux-concise, which already includes strings for all of the default handlers. From now on, we're going to be sticking with using HandlerTypes, because it gives us the autocomplete and makes it harder to make silly typos.

Actions

This concision is possible because of the basic assumptions that the default handlers make about the actions that the output reducer will receive. For the most part, they expect to recieve actions that follow the Flux Standard Action rules, with one exception.

Below are tables showing what actions are handled by default for each reducer creator and what needs to be included in each action.

Boolean Actions:

Handler Name	Type	Payload	Index
true	yes	no	no
false	yes	no	no
toggle	yes	no	no
reset	yes	no	no

Value Actions:

Handler Name	Type	Payload	Index
update	yes	yes	no
reset	yes	no	no

Array Actions:

Handler Name	Type	Payload	Index
push	yes	yes	no
pop	yes	no	no
updateIndex	yes	yes	yes
concat	yes	yes	no
clear	yes	no	no
filter	yes	yes	no
map	yes	yes	no
reset	yes	no	no

Object Actions:

Handler Name	Type	Payload	Index
update	yes	yes	no
reset	yes	no	no
clear	yes	no	no

Misc. Action Examples:

filterAction = {
  type: 'NO_CATS',
  payload: (elem, index) => elem !== 'cat'
}
 
updateIndexAction = {
  type: 'EDIT_COMMENT',
  index: 10,
  payload: 'new comment'
}

Customizing Your Reducers

While I've tried my best to include a lot of the most common use cases in redux-concise, there's more than likely going to be times where redux-concise doesn't include an action that you want to use. Because of this, I've included an extra parameter to all redux-concise reducers called customHandlers, which is an object in which you can include whatever custom action handler functions you want and use them in the same way you would use the standard, included handlers.

As an example, the standard push handler in redux-concise adds a value to the back of an array. Now, you want to add something to the front of the array instead. Here's how you would do it.

import { 
  createArrReducer, 
  HandlerTypes 
} from 'redux-concise'
 
ArrHandlerTypes = {
  ...HandlerTypes,
  addToFront: 'addToFront'
}
 
const reducer = createArrReducer([], {
  ADD_TO_FRONT: ArrHandlerTypes.addToFront
}, {
  addToFront: (state, action) => [action.payload, ...state]
})

Composition

Lets say we're trying to create a Twitter-like app. We might want to have a slice of state for a post that includes the user that create the post, the content of the post, as well as the comments associated with that post. Let's create this slice of state with our createObjRedcuer function. (Note that this wouldn't be an ideal way to shape this state. See the redux docs for more info, just using this as an example)

import { 
  createObjReducer, 
  HandlerTypes 
} from 'redux-concise'
 
const PostHandlerTypes = { 
  ...HandlerTypes, 
  addComment: 'addComment', 
  editComment: 'editComment
}
 
const post = createObjReducer({
  user: 'bheberer',
  content: 'hey there',
  comments: []
}, {
  EDIT_CONTENT: PostHandlerTypes.update,
  ADD_COMMENT: PostHandlerTypes.addComment,
  EDIT_COMMENT: PostHandlerTypes.editComment
}, {
  addComment: (state, action) => {
    ...state,
    comments: [...state.comments, action.payload]
  },
  editComment: (state, action) => {
    ...state,
    comments: Object.assign([...state.comments], {
    [action.index]:
      typeof action.payload === 'function'
        ? action.payload(state.comments[action.index])
        : action.payload
  })
  }
})

Because our comments array is contained within this state object, we have to manually add functionality in order to update it appropriately, or include it in the action that we send to the reducer. However, you may have noticed that we're basically just adding push and updateIndex functionality, which is already included in createArrReducer.

In order to utilize this already built-in functionality, I've introduced the concept of innerReducers to createObjReducer. innerReducers is an extra argument for createObjReducer that lets you use compeletely separate reducers for certain properties within your output state object. Let's create the same slice of state using innerReducers.

import { 
  createArrReducer,
  createObjReducer, 
  HandlerTypes 
} from 'redux-concise'
 
const comments = createArrReducer([], {
  ADD_COMMENT: HandlerTypes.push,
  EDIT_COMMENT: HandlerTypes.updateIndex
})
 
const post = createObjReducer({
  user: 'bheberer',
  content: 'hey there',
  comments: []
}, {
  EDIT_CONTENT: HandlerTypes.update
}, {
  /* This is where customHandlers would go */
}, {
  comments
})

Here, we've created a completely separate reducer for the comments array, and using the innerReducers argument, we're able to pipe it into the post reducer. Note that the reducer we're piping in has the same name as the property we're looking to control. Now we're able to utilize the functionality that createArrReducer provides, freeing us from having to write redundant code.

API

createValueReducer

const reducer = createValueReducer(
  (initialState: value),
  (actionTypes: Object),
  (customHandlers: Object)
)

Higher order function that accepts an initialState value, an object of action types that the reducer will handle, and an object of custom handler functions.

Default Action Handlers:

Name	Description
update	updates value with payload (can be value or function)
reset	reset value to initial state

Example usage:

import { 
  createValueReducer,
  HandlerTypes 
} from 'redux-concise'
 
const CounterHandlerTypes = { 
  ...HandlerTypes,
   increment: 'increment', 
   decrement: 'decrement' 
}
 
const counter = createValueReducer(0, {
  INCREMENT: CounterHandlerTypes.increment,
  DECREMENT: CounterHandlerTypes.decrement,
  RESET: CounterHandlerTypes.reset
}, {
  increment: (state, action) => action.payload + 1,
  decrement: (state, action) => action.payload - 1
})

createBoolReducer

const reducer = createBoolReducer(
  (initialState: value),
  (actionTypes: Object),
  (customHandlers: Object)
)

Higher order function that accepts an initialState value, an object of action types that the reducer will handle, and an object of custom handler functions.

Default Action Handlers:

Name	Description
true	sets boolean to true
false	sets boolean to false
toggle	toggles boolean value
reset	reset boolean to initial state

Example usage:

import { 
  createBoolReducer,
  HandlerTypes 
} from 'redux-concise'
 
const isFetching = createBoolReducer(false, {
  FETCHING: HandlerTypes.true,
  RECEIVED: HandlerTypes.false
})

createArrReducer

const reducer = createArrReducer(
  (initialState: value),
  (actionTypes: Object),
  (customHandlers: Object)
)

Higher order function that accepts an initialState value, an object of action types that the reducer will handle, and an object of custom handler functions.

Default Action Handlers:

Name	Description
push	push payload to end of array
pop	remove element from end of array
updateIndex	update element at index with payload (can be value or function)
concat	concatenate payload to end of array
clear	clear array
filter	filter array with payload function
map	map array with payload function
reset	reset array to initial state

Example usage:

import {
  createArrReducer,
  HandlerTypes
} from 'redux-concise'
 
const comments = createArrReducer([], {
  ADD_COMMENT: HandlerTypes.push,
  DELETE_COMMENT: HandlerTypes.filter,
  EDIT_COMMENT: HandlerTypes.updateIndex,
  DELETE_ALL_COMMENTS: HandlerTypes.clear
})

createObjReducer

const reducer = createObjReducer(
  (initialState: value),
  (actionTypes: Object),
  (customHandlers: Object),
  (innerReducers: Object)
)

Higher order function that accepts an initialState value, an object of action types that the reducer will handle, an object of custom handler functions and an object of reducers to be piped into the object.

Default Action Handlers:

Name	Description
update	spreads payload to state object
clear	empties state object
reset	reset object to initial state

Example usage:

import { 
  createArrReducer,
  createObjReducer, 
  HandlerTypes 
} from 'redux-concise'
 
const comments = createArrReducer([], {
  ADD_COMMENT: HandlerTypes.push,
  DELETE_COMMENT: HandlerTypes.filter,
  EDIT_COMMENT: HandlerTypes.updateIndex,
  DELETE_ALL_COMMENTS: HandlerTypes.clear
})
 
const post = createObjReducer({
  poster: 'bheberer',
  content: 'first',
  comments: []
}, {
  UPDATE_OP_USERNAME: HandlerTypes.update,
  EDIT_CONTENT: HandlerTypes.update,
  DELETE: HandlerTypes.clear
}, {
  /* This is where customHandlers would go */
}, {
  comments
})