20 NgRx Interview Questions and Answers

Prepare for the types of questions you are likely to be asked when interviewing for a position where NgRx will be used.

NgRx is a library for Angular that helps developers build reactive applications. It is used for state management, creating single source of truth, and for unidirectional data flow. If you are applying for a position that requires knowledge of NgRx, you should be prepared to answer questions about it during your interview. In this article, we will review some common NgRx questions and how you can answer them.

NgRx Interview Questions and Answers

Here are 20 commonly asked NgRx interview questions and answers to prepare you for your interview:

1. What is NgRx?

NgRx is a library for Angular that helps you manage state in your application. It provides a way for you to create reducers that manage your state, as well as an observable store that allows you to access your state from anywhere in your application. NgRx also provides a number of helper functions and directives to make working with state in Angular applications easier.

2. Can you explain the different parts of a state tree in NgRx?

The different parts of a state tree in NgRx include the reducer functions, the actions, and the selectors. The reducer functions are responsible for handling the state changes, the actions are responsible for dispatching the appropriate actions to the reducers, and the selectors are responsible for retrieving the appropriate data from the state tree.

3. What are actions and reducers in NgRx?

Actions are objects that contain information about what just happened in your application. Reducers are functions that take in the current state of your application and an action, and then return a new state object.

4. How does an action differ from a reducer in NgRx?

An action is a function that is used to trigger a change in the state of an application, while a reducer is a function that is used to handle the changed state. In other words, an action is used to initiate a change, while a reducer is used to actually implement the change.

5. What is a selector in NgRx?

A selector is a function that selects a slice of state from the store. Selectors can be used to create derived data, such as a filtered list of items or a sum of items.

6. Can you explain what an effect is in NgRx?

In NgRx, effects provide a way to isolate side effects from components and services. By using an effect, you can make sure that your component or service is only responsible for one thing. For example, if you have a component that needs to make a request to an API, you can use an effect to handle that request. This way, the component can focus on other things, and the effect can take care of the API request.

7. What is the purpose of entity adapters in NgRx?

Entity adapters are used to simplify the process of working with entities in NgRx. They provide a number of helper methods for performing CRUD operations on entities, as well as methods for selecting entities based on various criteria.

8. What do you understand about effects vs ngrx-entity in NgRx?

There are two main types of data in NgRx: entities and effects. Entities are the data that make up your application, while effects are the actions that can be taken on that data. In general, effects are used for asynchronous operations, while entities are used for synchronous operations.

9. What are some important mechanics of using NgRx?

NgRx is a library for Angular that helps to manage state in an application. When using NgRx, it is important to understand how to create actions, reducers, and selectors. Actions are used to describe what has happened in the application, and they are dispatched from components. Reducers take the actions and update the state accordingly. Selectors are used to select a slice of state from the store to be used in a component.

10. What are some real-world use cases for NgRx?

NgRx is a great tool for managing state in large-scale applications. It can be used to keep track of user data, application settings, and even application state.

11. When should I use selectors in my app?

Selectors are a powerful tool in NgRx, and they can be used in a variety of different ways. Generally speaking, you should use selectors any time you need to access data from the store outside of a component or effect. Selectors can be used to compute derived data, or to provide an easier way to access specific parts of the store.

12. How can you debug your store with Redux Dev Tools?

By default, the Redux DevTools are not enabled in production. However, you can enable them by setting the environment variable REACT_APP_ENABLE_REDUX_DEV_TOOLS to true. This will enable the DevTools and allow you to inspect the state of your store at any point in time.

13. What’s the difference between @ngrx/store, @ngrx/effects, and @ngrx/entity?

@ngrx/store is the library that provides the core Redux-like store for NgRx. @ngrx/effects is a library that provides a way to isolate side effects from your NgRx store. @ngrx/entity is a library that provides an easy way to manage entities in NgRx.

14. Why would you want to use NgRx instead of Angular services or RxJS Subjects?

NgRx provides a way to manage state in Angular applications. This can be helpful for a number of reasons, including making it easier to debug application state, providing a more predictable way to manage state, and making it easier to unit test state management code.

15. In NgRx, why would you want to use entities over plain arrays in your state?

Entities offer a few advantages over plain arrays when used in NgRx state. First, entities allow you to keep track of the entities by a key, which can be useful for looking up entities by id. Second, entities allow you to denormalize your data, which can improve performance when working with large data sets. Finally, entities offer a few helper methods for working with data, such as the ability to get the keys of all entities in the state.

16. What are some common mistakes developers make when working with NgRx?

Some common mistakes developers make when working with NgRx include not unsubscribing from observables, mutating state instead of creating immutable state objects, and not using the NgRx devtools.

17. What’s the best way to update nested objects in NgRx?

The best way to update nested objects in NgRx is to use the update operator. This operator will allow you to update specific parts of an object without having to replace the entire object.

18. What are some key benefits of using NgRx?

NgRx provides a way to manage state in Angular applications. It is a Redux-inspired state management library that is designed to work well with Angular. NgRx provides a few key benefits, including:

– simplifying state management by providing a single place to store all application state
– making it easier to debug applications by providing clear, concise Redux devtools
– providing a way to easily unit test state management logic
– making it easier to refactor code by providing well-defined reducers and action creators

19. Where do you put NgRx effects in your app?

NgRx effects can be placed anywhere in your app, but it is generally recommended to keep them in a separate file or module from your reducers and actions. This helps to keep your code organized and makes it easier to test your effects.

20. What are some good resources to learn more about NgRx?

There are a few different ways to learn more about NgRx. One way is to check out the NgRx website, which has a variety of resources including tutorials, guides, and sample code. Another way is to search for NgRx on online forums and message boards, where you can find helpful discussions and advice from other NgRx users. Finally, you can also find a number of NgRx books and online courses that can teach you everything you need to know about this popular state management library.


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