Middleware such as redux-thunk and redux-promise are examples of this.
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It also ensures that the UI will update as expected.Įxception: you may put non-serializable values in actions if the action will be intercepted and stopped by a middleware before it reaches the reducers. This ensures that capabilities such as debugging via the Redux DevTools will work as expected. Do Not Put Non-Serializable Values in State or Actions Īvoid putting non-serializable values such as Promises, Symbols, Maps/Sets, functions, or class instances into the Redux store state or dispatched actions.
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Strictly speaking, code such as console.log(state) is a side effect, but in practice has no effect on how the application behaves. If a reducer has side effects, this would cause those effects to be executed during the debugging process, and result in the application behaving in unexpected ways. For example, if you are doing time-travel debugging, reducer functions may be called many times with earlier actions to produce the "current" state value. The purpose of this rule is to guarantee that reducers will behave predictably when called. Note: It is acceptable to have a reducer call other functions that are defined outside of itself, such as imports from libraries or utility functions, as long as they follow the same rules. They must not execute any kind of asynchronous logic (AJAX calls, timeouts, promises), generate random values ( Date.now(), Math.random()), modify variables outside the reducer, or run other code that affects things outside the scope of the reducer function. Reducer functions should only depend on their state and action arguments, and should only calculate and return a new state value based on those arguments. Also, if you are using the Immer library for immutable updates, writing "mutating" logic is acceptable because the real data isn't being mutated - Immer safely tracks changes and generates immutably-updated values internally. Note: it is okay to modify copies of existing values - that is a normal part of writing immutable update logic. Use tools such as redux-immutable-state-invariant to catch mutations during development, and Immer to avoid accidental mutations in state updates.
Actual mutation of state values should always be avoided, both inside reducers and in all other application code. Mutating state is the most common cause of bugs in Redux applications, including components failing to re-render properly, and will also break time-travel debugging in the Redux DevTools.
Priority A Rules: Essential Do Not Mutate State
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That means you can feel free to make a different choice in your own codebase, as long as you're consistent and have a good reason. In these rules, we describe each acceptable option and suggest a default choice. Where multiple, equally good options exist, an arbitrary choice can be made to ensure consistency. Follow these rules whenever it is reasonably possible. Your code will still run if you violate them, but violations should be rare and well-justified. These rules have been found to improve readability and/or developer experience in most projects. Exceptions may exist, but should be very rare and only be made by those with expert knowledge of both JavaScript and Redux. These rules help prevent errors, so learn and abide by them at all costs. We've divided these rules into three categories: Priority A: Essential You are encouraged to follow these recommendations, but take the time to evaluate your own situation and decide if they fit your needs.įinally, we'd like to thank the Vue documentation authors for writing the Vue Style Guide page, which was the inspiration for this page. We also understand that team preferences vary and different projects have different requirements, so no style guide will fit all sizes.
With that in mind, we've put together this list of recommendations to help you avoid errors, bikeshedding, and anti-patterns. In addition, many developers have asked us to provide official guidance to reduce decision fatigue. However, time and experience have shown that for some topics, certain approaches work better than others.
There are many ways to use Redux, and much of the time there is no single "right" way to do things. It lists our recommended patterns, best practices, and suggested approaches for writing Redux applications.īoth the Redux core library and most of the Redux documentation are unopinionated. This is the official style guide for writing Redux code.
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