What are the things which we should never do inside a reducer?

## What are the things which we should never do inside a reducer?

### Answer:

Inside a reducer, which is a pure function used in Redux to specify how the application's state changes in response to actions, there are certain things that should never be done to ensure the proper functioning of the application. Some of these things include:

1. **Mutating the state directly:** It is crucial to always return a new state object instead of mutating the existing state object. This is because Redux relies on immutability to detect state changes and trigger re-renders efficiently.

2. **Performing asynchronous logic:** Reducers should be synchronous and pure functions, meaning they should not involve any side effects or asynchronous operations such as API calls. Asynchronous logic should be handled outside of the reducer, typically in middleware like Redux Thunk.

3. **Accessing the DOM or browser APIs:** Reducers should only depend on their input arguments (state and action) to compute the new state. They should not perform any operations that rely on external dependencies like the DOM or browser APIs, as this can lead to unpredictable behavior.

4. **Using non-serializable values in the state:** The state managed by Redux should be serializable, meaning it can be easily converted to a plain JavaScript object. Avoid storing complex data structures, functions, or non-serializable values in the state, as this can cause issues with serialization and debugging.

5. **Mixing business logic with state updates:** It's important to keep reducers focused on updating the state based on the action type, rather than implementing business logic. Business logic should be separated from reducer logic to improve code maintainability and reusability.

By following these guidelines and avoiding these common mistakes, developers can ensure that their reducers remain pure, predictable, and easy to reason about, leading to a more robust and efficient Redux application.

The company is the world’s best High Precision Machining, Spiral Bevel Gear, Gears for Petroleum Drilling Machinery supplier. We are your one-stop shop for all needs. Our staff are highly-specialized and will help you find the product you need.