FAQ.md

Redux FAQ

Table of Contents

• General

  • When should I learn Redux?
  • When should I use Redux?
  • Can Redux only be used with React?
  • Do I need to have a particular build tool to use Redux?

• Reducers

  • How do I share state between two reducers? Do I have to use combineReducers?
  • Do I have to use the switch statement to handle actions?

• Organizing State

  • Do I have to put all my state into Redux? Should I ever use React's setState()?
  • Can I put functions, promises, or other non-serializable items in my store state?
  • How do I organize nested or duplicate data in my state?
  • Should I put form state or other UI state in my store?

• Store Setup

  • Can or should I create multiple stores? Can I import my store directly, and use it in components myself?
  • Is it OK to have more than one middleware chain in my store enhancer? What is the difference between next and dispatch in a middleware function?
  • How do I subscribe to only a portion of the state? Can I get the dispatched action as part of the subscription?

• Actions

  • Why should type be a string, or at least serializable? Why should my action types be constants?
  • Is there always a one-to-one mapping between reducers and actions?
  • How can I represent “side effects” such as AJAX calls? Why do we need things like “action creators”, “thunks”, and “middleware” to do async behavior?
  • What async middleware should I use? How do you decide between thunks, sagas, observables, or something else?
  • Should I dispatch multiple actions in a row from one action creator?

• Immutable Data

  • What are the benefits of immutability?
  • Why is immutability required by Redux?
  • What approaches are there for handling data immutability? Do I have to use Immutable.JS?
  • What are the issues with using JavaScript for immutable operations?

• Using Immutable.JS with Redux

  • Why should I use an immutable-focused library such as Immutable.JS?
  • Why should I choose Immutable.JS as an immutable library?
  • What are the issues with using Immutable.JS?
  • Is Immutable.JS worth the effort?
  • What are some opinionated Best Practices for using Immutable.JS with Redux?

• Code Structure

  • What should my file structure look like? How should I group my action creators and reducers in my project? Where should my selectors go?
  • How should I split my logic between reducers and action creators? Where should my “business logic” go?
  • Why should I use action creators?
  • Where should websockets and other persistent connections live?

• Performance

  • How well does Redux “scale” in terms of performance and architecture?
  • Won't calling “all my reducers” for each action be slow?
  • Do I have to deep-clone my state in a reducer? Isn't copying my state going to be slow?
  • How can I reduce the number of store update events?
  • Will having “one state tree” cause memory problems? Will dispatching many actions take up memory?
  • Will caching remote data cause memory problems?

• Design Decisions

  • Why doesn't Redux pass the state and action to subscribers?
  • Why doesn't Redux support using classes for actions and reducers?
  • Why does the middleware signature use currying?
  • Why does applyMiddleware use a closure for dispatch?
  • Why doesn't combineReducers include a third argument with the entire state when it calls each reducer?
  • Why doesn't mapDispatchToProps allow use of return values from getState() or mapStateToProps()?

• React Redux

  • Why isn't my component re-rendering, or my mapStateToProps running?
  • Why is my component re-rendering too often?
  • How can I speed up my mapStateToProps?
  • Why don't I have this.props.dispatch available in my connected component?
  • Should I only connect my top component, or can I connect multiple components in my tree?

• Miscellaneous

  • Are there any larger, “real” Redux projects?
  • How can I implement authentication in Redux?