ArtsAutosBooksBusinessEducationEntertainmentFamilyFashionFoodGamesGenderHealthHolidaysHomeHubPagesPersonal FinancePetsPoliticsReligionSportsTechnologyTravel

Basics of Redux

Updated on March 29, 2017

What is Redux ???

Before we start Redux first we know Flux and Elm because redux internally uses these technologies.

Flux: Flux is the application architecture that Facebook uses for building client-side web applications.

Elm: Elm is a functional language that compiles to JavaScript.

Redux: Redux is a Flux implementation that remove complicity of flux and use the Elm logic, the basic idea of redux is the entire application state is kept on single store, redux run in different environment (Clint, Server, Native).

Core concept of Redux

  • State
  • Action
  • Store
  • Pure/Impure functions
  • Reducer


In redux, all the application state is stored as a single object, its a good idea to think of its shape before writing any code, the shape of state is up to you it can be array, object, or whatever you want, the state object in redux is immutable / read only, you cannot mutate the state object but return the new object if state changes.


Action is plain JavaScript object, actions are payloads of information that send data from your application to your store, the structure of object is up to you, action must have a type property that indicates the type of action being performed, type should typically be defined as string constants.


A store holds the whole state tree of your application, the only way to change the state inside it is to dispatch an action on it, a store is not a class, It's just an object with a few methods on it.

List of store methods.

  • getState
  • dispatch
  • subscribe
  • replaceReducer

Pure/Impure functions

Pure functions: A pure function doesn't depend and doesn't modify the states of variables out of its scope, doesn't have any side effect, doesn't have any observable like (Network access, DB call), doesn't modify the value that is pass as argument.

Impure functions: They may have side effect, maybe access network or perform curd operation, operate the DOM, they may overwrite the value that you as argument.


Reducers are just pure functions that take two arguments and return the next state.


  • Previous State.
  • Action.

Remember to return new state objects, instead of mutating the previous state, you can start with a single reducer, and as your app grows, split it off into smaller reducers that manage specific parts of the state tree.

Principal of Redux

Three principal of Redux.

  1. Single source of truth.
  2. State is read only.
  3. Changes are made with pure functions.

Single source of truth

The state of your whole application is stored in an object tree within a single store,
this makes it easy to create universal apps, a single state tree also makes it easier to debug or inspect an application, it also enables you to persist your app's state in development, for a faster development cycle.

State is read only

The only way to change the state is to emit an action, an object describing what happened.

Changes are made with pure functions.

To specify how the state tree is transformed by actions, you need to write pure reducers.


    0 of 8192 characters used
    Post Comment

    No comments yet.


    This website uses cookies

    As a user in the EEA, your approval is needed on a few things. To provide a better website experience, uses cookies (and other similar technologies) and may collect, process, and share personal data. Please choose which areas of our service you consent to our doing so.

    For more information on managing or withdrawing consents and how we handle data, visit our Privacy Policy at:

    Show Details
    HubPages Device IDThis is used to identify particular browsers or devices when the access the service, and is used for security reasons.
    LoginThis is necessary to sign in to the HubPages Service.
    Google RecaptchaThis is used to prevent bots and spam. (Privacy Policy)
    AkismetThis is used to detect comment spam. (Privacy Policy)
    HubPages Google AnalyticsThis is used to provide data on traffic to our website, all personally identifyable data is anonymized. (Privacy Policy)
    HubPages Traffic PixelThis is used to collect data on traffic to articles and other pages on our site. Unless you are signed in to a HubPages account, all personally identifiable information is anonymized.
    Amazon Web ServicesThis is a cloud services platform that we used to host our service. (Privacy Policy)
    CloudflareThis is a cloud CDN service that we use to efficiently deliver files required for our service to operate such as javascript, cascading style sheets, images, and videos. (Privacy Policy)
    Google Hosted LibrariesJavascript software libraries such as jQuery are loaded at endpoints on the or domains, for performance and efficiency reasons. (Privacy Policy)
    Google Custom SearchThis is feature allows you to search the site. (Privacy Policy)
    Google MapsSome articles have Google Maps embedded in them. (Privacy Policy)
    Google ChartsThis is used to display charts and graphs on articles and the author center. (Privacy Policy)
    Google AdSense Host APIThis service allows you to sign up for or associate a Google AdSense account with HubPages, so that you can earn money from ads on your articles. No data is shared unless you engage with this feature. (Privacy Policy)
    Google YouTubeSome articles have YouTube videos embedded in them. (Privacy Policy)
    VimeoSome articles have Vimeo videos embedded in them. (Privacy Policy)
    PaypalThis is used for a registered author who enrolls in the HubPages Earnings program and requests to be paid via PayPal. No data is shared with Paypal unless you engage with this feature. (Privacy Policy)
    Facebook LoginYou can use this to streamline signing up for, or signing in to your Hubpages account. No data is shared with Facebook unless you engage with this feature. (Privacy Policy)
    MavenThis supports the Maven widget and search functionality. (Privacy Policy)
    Google AdSenseThis is an ad network. (Privacy Policy)
    Google DoubleClickGoogle provides ad serving technology and runs an ad network. (Privacy Policy)
    Index ExchangeThis is an ad network. (Privacy Policy)
    SovrnThis is an ad network. (Privacy Policy)
    Facebook AdsThis is an ad network. (Privacy Policy)
    Amazon Unified Ad MarketplaceThis is an ad network. (Privacy Policy)
    AppNexusThis is an ad network. (Privacy Policy)
    OpenxThis is an ad network. (Privacy Policy)
    Rubicon ProjectThis is an ad network. (Privacy Policy)
    TripleLiftThis is an ad network. (Privacy Policy)
    Say MediaWe partner with Say Media to deliver ad campaigns on our sites. (Privacy Policy)
    Remarketing PixelsWe may use remarketing pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to advertise the HubPages Service to people that have visited our sites.
    Conversion Tracking PixelsWe may use conversion tracking pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to identify when an advertisement has successfully resulted in the desired action, such as signing up for the HubPages Service or publishing an article on the HubPages Service.
    Author Google AnalyticsThis is used to provide traffic data and reports to the authors of articles on the HubPages Service. (Privacy Policy)
    ComscoreComScore is a media measurement and analytics company providing marketing data and analytics to enterprises, media and advertising agencies, and publishers. Non-consent will result in ComScore only processing obfuscated personal data. (Privacy Policy)
    Amazon Tracking PixelSome articles display amazon products as part of the Amazon Affiliate program, this pixel provides traffic statistics for those products (Privacy Policy)