Redux Interview Questions And Answers

Redux has been here since 2015 by Dan Abramov and Andrew Clark. It is a platform that is nothing, but an open-source library made with the help of the scripting language JavaScript. The primary use of Redux is the management and centralization of the application state. Generally, you can use it with JavaScript libraries. For example, Angular or React, for building user interfaces. The fundamental principle of Redux is that it helps programmers achieve consistency throughout the apps they build, making debugging easier and making testing. The need for Redux professionals is rising significantly, which has led to the development of Redux interview questions and answers.

Redux helps to make the application test easier. This platform can perform with any layer of the user interface and consists of several larger add-on ecosystems that will be all according to the users’ needs. If put in simple words, Redux is a store-to-store state of the app variables. Redux will create the procedures and process to interact with the store so that the components will not only update or read the store.

Know More About Redux

The architecture of the Flux somewhat inspires the architecture of the Redux by Meta. Developers can centralize the state and logic of the application. Due to this, you can use Redux to unlock the wide range of amazing capabilities, for instance, Redo and Undo, state persistence, etc. It also provides a wide range of add-ons that can work with all types of User Interfaces. The development tools that this platform provides can help to debug the application.

There are various reasons to use Redux, such as one can easily manage the state of the application since the state is global. It will also help the components communicate without sending any props from one component to another. Redux will organize the codebase so that Redux experts can understand the application structure, which helps to test and debug the code easily.

Generally. you can use Redux with libraries Angular and React. With the help of these combinations, it will be possible to develop UI interfaces that depend on the desired state. And although you can write an application with the framework, once the app becomes complex, using the framework will manage the ever-growing component list and states, making the application tricky, if not impossible.

When it comes to programming, you can use the Redux apps, where you can share the data amongst the components. For instance, you will have an application that uses the login component. Moreover, you can share the data from the login component with the status component. Let us look at some of the tough Redux interview questions.

What Is React?

React Is a Declarative, Efficient, Flexible Open-Source Front-End JavaScript Library Developed by Facebook In 2011. It Follows the Component-Based Approach For Building Reusable UI Components, Especially For Single Page Application. You can use it for Developing Interactive View Layers Of Web And Mobile Apps. Jordan Walke, A Software Engineer At Facebook made it. It Was Initially Deployed On Facebook’s News Feed Section In 2011 And Later Used In Its Products Like WhatsApp & Instagram.

Differentiate Between Real DOM And Virtual DOM.

React Uses Virtual DOM. Below Is The Difference Between Real And Virtual DOM.
REAL DOM
1. It Updates slowly.
2. Can Directly Update HTML.
3. Creates A New DOM If Element Updates.
4. DOM Manipulation Is Very Expensive.
5. Too Much Of Memory Wastage.
VIRTUAL DOM
1. It Updates Faster.
2. Can’t Directly Update HTML.
3. TUpdates The JSX If Element Updates.
4. DOM Manipulation Is Very Easy.
5. No Memory Wastage.

What Are The Features Of React?

React Framework Gaining Quick Popularity As The Best Framework Among Web Developers. The Main Features Of React Are:
1. JSX
2. Components
3. It Follows Unidirectional Data Flow Or One-Way Data Binding
4. Virtual DOM
5. Simplicity
6. Performance
7. It Uses Server-Side Rendering

What Are Advantages of React?

1. Reusable Components
2. Performance Enhancement
3. The Support Of Handy Tools
4. Known To Be SEO Friendly
5. The Benefit Of Having JavaScript Library
6. Easy To Learn And USe
7. Scope For Testing The Codes
8. You can conveniently use it on the client as well as server side
9. Using React, Writing UI Test Cases Become Extremely Easy
10. Because Of JSX, Code’s Readability Increases

Define Redux Thunk?

It is known as middleware that permits you to mark achievement creators that revisit a function in its place of an act. You can use the Thunk to hold up the post of an action. The internal function receives the layup methods to transmit and get state () as parameters.

Name some features of Redux Dev tools.

Some of the features are:

  • Lets you go backside in time by “cancelling” measures.
  • If the reducers toss, you will see throughout which act this happened, and what the mistake was
  • Let’s examine every state and action freight.
  • If you modify the reducer code, each “staged” accomplishment will be re-evaluated.

What Are The Limitations Of React?

– React Is Just a Library, Not A Full-Blown Framework
– Coding Gets Complex as It Uses Inline Templating And JSX
– View Part
– Its Library Is Very Large and Takes Time to Understand

Why would you use force update in a React?

In order to power a re-render if there is some form, React is not detecting that requires a revision to the UI.

State the difference between a controlled compound and uncontrolled component?

The difference between them is:

  • A controlled component is a component where React is in power and is the single source of fact for the form data.
  • An uncontrolled component is where your form data is handled by the DOM, in its place of within your React component.

Tell me the redux workflow features?

  • Reset: Allow resetting the state of the store
  • Revert: Rollback to the last dedicated state
  • Sweep: You can attach all disabled actions that you might have fired by error.
  • commit: makes the present state the initial state.

What Is JSX?

JSX Is A Shorthand For JavaScript XML. This Is A Type Of File Used By React Which Utilizes The Expressiveness Of JavaScript Along With HTML Like Template Syntax. This Makes The HTML File Really Easy To Understand. This File Makes Applications Robust And Boosts Its Performance.

Why Can’t Browsers Read JSX?

Browsers Can Only Read JavaScript Objects But JSX Is Not A Regular JavaScript Object. Thus To Enable A Browser To Read JSX, First, We Need To Transform JSX File Into A JavaScript Object Using JSX Transformers Like Babel And Then Pass It To The Browser.

How Is React Different From Angular?

ARCHITECTURE – React Have Only The View Of MVC Where Angular Have Complete MVC
RENDERING – React Have Server-Side Rendering Where Angular Have Client-Side Rendering
DOM – React Uses Virtual DOM Where Angular Uses Real DOM
DATA BINDING – React Have One-Way Data Binding Where Angular Have Two-Way Data Binding
DEBUGGING – React Have Compile Time Debugging Where Angular Have Runtime Debugging
AUTHOR – React By Facebook Where Angular By Google
TYPE – React Is Open Source JS Framework Where Angular Is Open Source MVC Framework
PERFORMANCE – React Is Fast, Due To Virtual DOM Where Angular Is Slow
TESTING – React Support Unit Testing Where Angular Support Unit And Integration Testing

Explain The Purpose Of Render() In React.

Each React Component Must Have A Render() Mandatorily. It Returns A Single React Element Which Is The Representation Of The Native DOM Component. If More Than One HTML Element Needs To Be Rendered, Then They Must Be Grouped Together Inside One Enclosing Tag Such As Form, Group, Div Etc. This Function Must Be Kept Pure I.E., It Must Return The Same Result Each Time It Is Invoked.

What Is Props?

Props Is The Shorthand For Properties In React. They Are Read-Only Components Which Must Be Kept Pure I.E. Immutable. They Are Always Passed Down From The Parent To The Child Components Throughout The Application. A Child Component Can Never Send A Prop Back To The Parent Component. This Help In Maintaining The Unidirectional Data Flow And Are Generally Used To Render The Dynamically Generated Data.

What Is A State In React?

States Are The Heart Of React Components. States Are The Source Of Data And Must Be Kept As Simple As Possible. Basically, States Are The Objects Which Determine Components Rendering And Behavior. They Are Mutable Unlike The Props And Create Dynamic And Interactive Components. They Are Accessed Via This.State().

Differentiate Between States And Props.

States
– Receive Initial Value From Parent Component
– Parent Component Can’t Change Value
– Set Default Values Inside Component
– Changes Inside Component
– Set Initial Value For Child Components
– Cant Changes Inside Child Components
Props
– Receive Initial Value From Parent Component
– Parent Component Can Change Value
– Set Default Values Inside Component
– Cant Changes Inside Component
– Set Initial Value For Child Components
– Hanges Inside Child Components

What Is Arrow Function In React? How Is It Used?

Arrow Functions Are More Of Brief Syntax For Writing The Function Expression. They Are Also Called ‘Fat Arrow‘ (=>) The Functions. These Functions Allow To Bind The Context Of The Components Properly Since In ES6 Auto Binding Is Not Available By Default. Arrow Functions Are Mostly Useful While Working With The Higher Order Functions.

Differentiate Between Stateful And Stateless Components.

Stateful Component
– Stores Info About Component’s State Change In Memory
– Have Authority To Change State
– Contains The Knowledge Of Past, Current And Possible Future Changes In State
– Stateless Components Notify Them About The Requirement Of The State Change, Then They Send Down The Props To Them.
Stateless Component
– Calculates The Internal State Of The Components
– Do Not Have The Authority To Change State
– Contains No Knowledge Of Past, Current And Possible Future State Changes
– They Receive The Props From The Stateful Components And Treat Them As Callback Functions.

What Are The Different Phases Of React Component’s Lifecycle?

There Are Three Different Phases Of React Component’s Lifecycle:
– Initial Rendering Phase: This Is The Phase When The Component Is About To Start Its Life Journey And Make Its Way To The DOM.
– Updating Phase: Once The Component Gets Added To The DOM, It Can Potentially Update And Re-Render Only When A Prop Or State Change Occurs. That Happens Only In This Phase.
– Unmounting Phase: This Is The Final Phase Of A Component’s Life Cycle In Which The Component Is Destroyed And Removed From The DOM.

Explain The Lifecycle Methods Of React Components In Detail.

– ComponentWillMount() – Executed Just Before Rendering Takes Place Both On The Client As Well As Server-Side.
– ComponentDidMount() – Executed On The Client Side Only After The First Render
– ComponentWillReceiveProps() – Invoked As Soon As The Props Are Received From The Parent Class And Before Another Render Is Called.
– ShouldComponentUpdate() – Returns True Or False Value Based On Certain Conditions. If You Want Your Component To Update, Return True Else Return False. By Default, It Returns False.
– ComponentWillUpdate() – Called Just Before Rendering Takes Place In The DOM.
– ComponentDidUpdate() – Called Immediately After Rendering Takes Place.
– ComponentWillUnmount() – Called After The Component Is Unmounted From The DOM. It Is Used To Clear Up The Memory Spaces.

What do you mean by redux-saga?

It is a documentation that aims to make elevation effects in redux applications easier and superior. It is obtainable in NPM as:

npm install --save redux-saga

What do you mean by redux selectors and why to use them?

Selectors are functions that obtain redux state as a dispute and revisit some data to pass to the constituent. For example:

const getUserData = state => state.user.data;

How do you select the initial state in Redux?

You need to exceed the initial state as a second dispute to “create a store.”

const rootReducer = combineReducers({
  todos: todos,
  visibilityFilter: visibilityFilter
});

 
const initialState = {
  todos: [{id:123, name:'sudheer', completed: false}]
};

const store = createStore(
  rootReducer,
  initialState
);

How do you access the redux store outside a react component?

You need to sell the store overseas from the component where it was shaped with creating the store. Also, it shouldn’t infect the global window object.

store = createStore(myReducer);
export default store;

What Is An Event In React?

In React, Events Are The Triggered Reactions To Specific Actions Like Mouse Hover, Mouse Click, Key Press, Etc.But There Are Some Syntactical Differences Like:
– Events Are Named Using Camel Case Instead Of Just Using The Lowercase.
– Events Are Passed As Functions Instead Of Strings.

What Do You Understand By Refs In React?

Refs Is The Shorthand For References In React. It Is An Attribute Which Helps To Store A Reference To A Particular React Element Or Component, Which Will Be Returned By The Components Render Configuration Function. It Is Used To Return References To A Particular Element Or Component Returned By Render(). They Come In Handy When We Need DOM Measurements Or To Add Methods To The Components.

What Are Class Components?

These Types Of Components Can Hold And Manage Their Own State And Have A Separate Render Method To Return JSX On The Screen. They Are Also Called Stateful Components As They Can Have A State.

What Is The Flux?

Flux Is the Application Architecture That Facebook Uses for Building Web Applications. It Is a Method of Handling Complex Data Inside a Client-Side Application and Manages How Data Flows in a React Application.

There Is a Single Source of Data (The Store) And Triggering Certain Actions Is the Only Way to Update Them. The Actions Call the Dispatcher, And Then the Store Is Triggered and Updated with Their Own Data Accordingly
When A Dispatch Has Been Triggered, And the Store Updates, It Will Emit a Change Event That the Views Can Retender Accordingly.

How Is Redux Different From Flux?

Redux-
– Redux Is An Open-Source JavaScript Library Used To Manage Application State
– Store’s State Is Immutable
– Can Only Have A Single-Store
– Uses The Concept Of Reducer
Flux-
– Flux Is An Architecture And Not A Framework Or Library
– Store’s State Is Mutable
– Can Have Multiple Stores
– Uses The Concept Of The Dispatcher

What Is Major Differences Between The ES5 And ES6

Require Vs. Import – The Require Used In ES5 Is Now Replaced With Import. Var React = Require(‘React’); //Is Now Replaced With Import React From ‘React’; //In ES6
Export Vs. Exports – Instead Of Exports, Now Export Is Used.Export Default Component; // Replaces Module.Exports = Component; // In ES6
Component And Function – The Use Of Component And Function Has Also Changed From ES5 To ES6.

You Must’ve Heard That “In React, Everything Is A Component.” What Do You Understand From The Statement?

The Building Blocks Of A React Application’s UI Are Called Components. Any App UI Created Using React Is Divisible Into A Number Of Small Independent And Reusable Pieces, Known As Components. React Renders Each Of The Components Independent Of Each Other. Hence, There Is No Effect Of Rendering A Component On The Rest Of The App UI.

Can Parent Components Change Value in States and Props?

The Parent Component Can Change The Value In Props But Not In The State.

Can Changes Be Made Inside The Component?

The Changes Can Be Made Inside The State But Not In Props.

Can We Make Changes Inside Child Components?

Yes, We Can Make Changes Inside The Child Component In Props But Not In The Case Of States.

Define Synthetic Events in React?

36 Define Synthetic Events In React?

The Synthetic Events in React Are the Objects in React, Which Acts as a Cross-Browser Wrapper Around the Browser’s Native Event. The Main Purpose is to Combine the Different Browsers on the API So That the Event Shows Various Properties.

Can We Modularize Code In React? How?

Yes, We Can Modularize Code In React. It Can Be Done By Using Export And Import Properties.

Why do ReactJs use class names over class attributes?

A class is a keyword in Javascript and JSX is an addition of Javascript. That’s the major reason why React uses class Name as a replacement for class.

render() {
  return Menu
}

What is the difference between React context and React redux?

You can use Context in your application directly and is going to be great for passing down data to deeply nested components which is what it was designed for. Whereas Redux is much more powerful and provides a large number of features that the Context Api doesn’t provide.

Also, React Redux uses context internally but it doesn’t expose this fact in the public API. So, you should feel much safer using context via React Redux than directly because if it changes, the burden of updating the code will be on React Redux instead of developer responsibility.

Are there any similarities between Redux and RxJS?

These libraries are very different for very different purposes, but there are some vague similarities.

  • Redux is a tool for managing state throughout the application. It is usually used as an architecture for UIs. Think of it as an alternative to (half of) Angular.
  • RxJS is a reactive programming library. It is usually used as a tool to accomplish asynchronous tasks in JavaScript. Think of it as an alternative to Promises.

Redux uses the Reactive paradigm a little bit because the Store is reactive. The Store observes actions from a distance and changes itself. RxJS also uses the Reactive paradigm, but instead of being an architecture, it gives you basic building blocks, Observables, to accomplish this “observing from a distance” pattern.

What Is The Difference Between Element And Component?

Element – A Plain Object Describing What We Want to Appear on the Screen in Terms of the DOM Nodes / Other Components. Elements Can Contain Other Elements in Their Props. Creating A React Element Is Cheap. Once An Element Is Created, It Is Never Mutated.
– Component – Declared in Several Ways. Component Can Class with a Render() Method. Alternatively, It Can Be Defined as a Function. Component Takes Props as an Input, And Returns an JSX Tree as the

What Is The Super Keyword In React?

The Super Keyword Is Used To Access & Call Functions On An Object’s Parent.

What Is Meant By Callback Function? What Is Its Purpose?

A Callback Function Should Be Called When SetState Has Finished, And The Component Is Re-Rendered. As The SetState Is Asynchronous, Which Is Why It Takes In A Second Callback Function.

Explain Error Boundaries?

Error Boundaries Help You To Catch Javascript Error Anywhere In The Child Components. They Are Most Used To Log The Error And Show A Fallback UI.

What Is the Use of Empty Tags <>?

Empty Tags Are Used In React For Declaring Fragments.

What Is The Use Of Webpack?

Webpack In Basically Is A Module Builder. It Is Mainly Runs During The Development Proc

What Is Babel in React Js?

Babel, Is A JavaScript Compiler That Converts Latest JavaScript Like ES6, ES7 Into Plain Old ES5 JavaScript That Most Browsers Understand.

Explain The Term Reconciliation

When A Component’s State Or Props Change Then Rest Will Compare The Rendered Element With Previously Rendered DOM And Will Update The Actual DOM If It Is Needed. This Process Is Known As Reconciliation.

Explain The Meaning Of Mounting And Demounting

The Process of Attaching the Element to the DCOM Is Called Mounting.
The Process of Detaching the Element from The DCOM Is Called the Is demounting Process

What is the typical flow data in a React+ Redux app?

Call-back from UI components dispatches an act with a payload; these dispatched actions are intercepted and established by the reducers. This interception will produce a new application state. From here, the actions will be propagated down through a ladder of components from the Redux store.