Top NgRX Interview Questions (2021) | TechGeekNxt >>

Top NgRX Interview Questions (2021)

  1. What is NgRx?
  2. What is NgRx state management?
  3. What Is Reactive Programming?
  4. What is NgRX Store Module?
  5. What is store in NgRx?
  6. What is Reducer in NgRx?
  7. What are Actions in NgRx?
  8. What is Dispatcher in NgRx?
  9. What is Middleware in NgRx
  10. What is NgRx Selectors?
  11. Explain how the various ngrx/store elements, such as Store, State, Reducer, Action, and Component, communicate with one another?
  12. What are the advantages of using the NgRX Store Module?

Q: What is NgRx?
Ans:

NgRx stands for Angular Reactive Extensions, NgRx Store provides reactive state management for Angular apps inspired by Redux. NgRx has libraries for managing both global and local state. Isolation of side effects in order to achieve a more streamlined component architecture. Developer tooling that makes it easier for developers to construct a variety of applications.

Q: What is NgRx state management?
Ans:

Inside the NgRX Store, a state is represented by a single JavaScript object. The state is either read-only or immutable. This means that there isn't a direct Store API for changing the Store's state object.

const state = {
    employees: []
};

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Q: What Is Reactive Programming?
Ans:

Reactive programming is a means for your programmes to handle events and data flow. Instead of asking for changes, reactive programming allows you to design your components and other pieces of software to react to them.

RxJS is an excellent tool for reactive programming, as you may know.

Q: What is NgRX Store Module?
Ans:

The NgRX Store module is an Angular state management library. It's based on the popular Redux React state management library. The NgRX Store imports Redux's state management concepts and adds RxJS to enable an observable means of communication throughout the Store APIs, giving Angular developers a familiar experience with Angular app development.

Q: What is store in NgRx?
Ans:

A Store contains the application state. In the ngrx/store module, the Store works as a container for the state. Additionally, to build the communication channel, Angular components inject the Store into their constructors. Angular components utilize two methods exposed by the Store. A component can gain access to the following functions by injecting the Store:

  1. select() : This function is used by the Store to return a slice of state data from the Store's state. It returns the Store object, which is an Observable, so that components can hook into the select() method to monitor state changes as the Store constructs a new state object.
  2. dispatch() : This function is used by the Store to allow components to send actions to the Store. A payload could be included in an action as an option. The Store is in charge of the action that was dispatched via a reducer.

Q: What is Reducer in NgRx?
Ans:

Action Reducer or Reducer are pure functions in terms of a state management library. Reducers respond to actions by returning a new state object that incorporates all of the changes made to the state, resulting in the state's immutability.

The reducer examines the action dispatched, reads the action's payload, performs the appropriate action on the state within the Store, and produces a new state object containing all of the changes. A reducer could be something like this:

function reducer(state: State, action: Action) {
    const actionType = action.type;
    const employee= action.payload;

    switch (actionType) {
        case 'ADD_EMPLOYEES': {
            const employees= [...state.employees, employee];
            return { employees}
        }
        ...
    }
}

Q: What are Actions in NgRx?
Ans:

The application must dispatch an action in order to update the state of a Store. A reducer, also known as a pure function, identifies this action, updates the state, and returns a new, immutable state object. As an example of an action, consider the following:

const action = {
    type: 'ADD_EMPLOYEES',
    payload: {
        name: 'John',
        competency: ['ASP.NET', 'Angular']
    }
};

Q: What is Dispatcher in NgRx?
Ans:

Dispatchers are just a way as an entry point to start dispatching your action. A dispatch method is available on the store in Ngrx.

Q: What is Middleware in NgRx?
Ans:

It is a set of functions that intercept each action that is dispatched in order to produce side effects. They're part of the Ngrx/Effect library.

Q: What is NgRx Selectors?
Ans:

Selectors are pure functions that receive state slices as input parameters and return state data slices for components to consume. The Selectors are the ngrx/store module's query tools, similar to how databases have their own SQL query language.

Every Feature module in an Angular application is responsible for injecting its own state into the root application state. As a result, the state is a tree of properties with sub-properties, and so on. To avoid manually traversing the state tree every time the Store composes a new state and informs components, you define selectors at different levels of the state tree.

Below example uses a query and return the array of Employees from the state using a selector:

export const getAllEmployees =
    createSelector(getState, (state): Employees[] => {
        return state && state.employees;
    }
);

....
....

this.store.select<Employees[]>(getAllEmployees).subscribe(
    employees=> console.log(developers)
);

Q: Explain how the various ngrx/store elements, such as Store, State, Reducer, Action, and Component, communicate with one another?
Ans:

An Angular component dispatches an action to the Store, which initiates the cycle. The action is captured by the Store, which then performs the reducers. As a result, a new composed state is created and saved in the Store. Only then does the Store inform all related components with the stat modifications that a new state is available and ready for use.

NgRX Components

The one-way data flow between the components simplifies and solves the complexity that occurs from not having a Store and depending solely on components talking with services to read and update the application state.

Q: What are the advantages of using the NgRX Store Module?
Ans:

Below ar the

  1. The Store keeps track of the state, allowing the developer a single point of truth from which to query and alter the application's state.
  2. The ngrx/store module prioritises testability. Reducers and selectors are pure functions, therefore testing them is straightforward. Actions are also simple JavaScript objects that may be mocked to create a testing scenario.
  3. The ngrx/store module helps manage the state of both the Root and Feature modules. Users can choose to build an Angular app with either Lazy Loading or Eager Loading modules with the ngrx/store module.
  4. Performance benefits using ngrx/store module in an Angular application.


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