React Interview Questions: Everything You Need to Know
Are you searching for React interview questions? You have come to the right place! Here, you'll find all the latest and most relevant React Interview questions and answers.
Written by RamotionApr 26, 202330 min read
Last updated: Aug 29, 2024
React has become the most popular JavaScript library/framework. Although its first appearance date is 2013, now React is used by at least half of the websites on the Internet. The demand for developers who know how to work with React is growing rapidly. This article will help you prepare for a React interview. Below you will find a list of questions asked to candidates during a real interview and answers to these questions are also provided. If you are a react js developer looking for an interview, this article will also be useful for you. You can use these questions as practice material and prepare for your next interview.
The list of questions will be useful for both junior and senior developers. If you are a beginner, it will help you understand how to answer interview questions on React. For senior developers, these questions will be a great opportunity to test their knowledge and practice answering tricky technical questions.
Introduction
Since React is an open-source library, it has gained a lot of global acceptance and has been used in a lot of big projects. As a result, there is also an increasing demand for developers who are skilled in using this library for job positions. What's more, as per studies and statistics React is set to rise further!
React has been a hot topic in the Web Development community ever since Meta open-sourced back in 2013. But what is React exactly? More importantly, why React and not another JavaScript framework? What are some of the advantages and disadvantages of using React instead of other frameworks like Angular, Backbone, Knockout, or Vue.js? Before we take a look at those questions, let's see what exactly React is and how it can help us build UIs.
What is React?
React is a JavaScript library for building user interfaces. It's used at Facebook, Instagram, Netflix, and many other companies.
React makes it painless to create interactive components and UIs. Design simple views for each state in your application, and React will efficiently update and render just the right components when your data changes. Declarative views make your code more predictable, readable, and concise. And React comes with powerful features like server-side rendering, time-travel debugging, and integrated unit testing.
Learning React is a great way to get started with modern web development. You'll learn how to build applications that load quickly and run smoothly across a broad range of devices. You'll build composable UI components that can be reused anywhere within a React application while reusing logic in a single place (the store).
React has gained a lot of popularity over the last few years because it's simple to use, easy to learn, and allows developers to create reusable UI components.
The core idea behind React is that your UI should be defined as a hierarchy of components that are reusable across different applications and websites. When something changes in the data, only the relevant parts need to update — this helps maintain high performance when rendering user interfaces on the fly.
Advantages and Disadvantages of React
Advantages
- It’s easy: React is a very simple concept to grasp and it's easy to get started with. It has a very low learning curve, which means that you can get up and running quickly without having to be an expert in front-end development.
- It's fast: React uses a one-way data flow, in which changes trigger updates within the UI but not vice versa. This makes React components extremely fast! The same approach is crucial to building progressive web apps—apps that load quickly and work when offline. It can handle thousands of DOM updates per second, even on mobile devices. The performance is what makes it ideal for developing complex applications like games and AR/VR experiences.
- It supports JSX: JSX allows you to write HTML code directly into your JavaScript files without having to use special XML syntax or anything like that—just write normal HTML code.
- It's modular: React components are easy to create, reuse, test, and compose - all without having to compromise on performance. This makes it perfect for building complex applications.
Disadvantages
- It's not a good choice if you're building something simple, like a static site.
- It’s not a framework: React is just the view layer. This means that you need to write your own code for handling routing, state management, and AJAX calls.
- It’s difficult to debug code when multiple components are involved; you need to understand how props and state work together in order to diagnose bugs.
- There are no design patterns: there are no default ways to structure your application. This can be a bit of a problem for beginners, but it also means that you have more freedom to choose the best way to organize your code.
- It’s not good for building large applications: React is not intended for building complex UIs or websites with thousands of lines of code. You need to use other libraries like Redux or MobX in order to manage yo
Top React Interview Questions and Answers
1. How to create a new React app with CRA?
The easiest way to get started with React and webpack is to use Create React App (CRA), which can be used to quickly generate a project with all of the necessary configuration.
Before that make sure you have Node >= 14.0.0 and npm >= 5.6 installed on your machine.
Run this command in your terminal to create a new react app:
npx create-react-app my-awesome-app
Then you can start the project like this:
cd my-awesome-app
npm start
2. Functional components vs Class components
Functional Component
A functional component is a special type of React component that provides a simpler way to create, compose and reuse functional stateless components.
It has one advantage over the old-school class-based components. The state of the component is immutable, which means that you cannot change it during its lifecycle. This also means that it behaves more like a pure component than any other type of component, which makes it easier to reason about your code.
Functional components in React don't have a state. They don't have any lifecycle methods. They can't be mounted or unmounted. All these make them easier to test and simpler to reason about.
But with the introduction "Hooks", it's possible to create stateful functional components. You can store a value in this new state, and you can update it by using the useState hook. This is very useful if you need to keep track of something that changes over time (like an animation), or if you want to make sure your component always has some initial value when it mounts.
Example of functional component:
function App() {
return <h1>Hello World!</h1>;
}
// or with arrow function
const App = () {
return <h1>Hello World!</h1>;
}
Class Component
Class components are the way to go if you need fine-grained control over how the component state is managed. They work well when you have multiple instances of your component in the application and need to manage their internal state separately. You can think of them as an object-oriented alternative to functional components, which are best suited for simple applications that don’t need a lot of state management.
Class components are useful if you need to dynamically access properties of the state, or if you want to manage the internal state of multiple instances of your component independently from each other. Functional components with state management via context In contrast to class components, functional components don’t have their own isolated states. Instead, they rely on props for all data required by them.
Class components use the render() method to return JSX.
Example of class component:
import React from "react";
class App extends React.Component {
render() {
return <h1>Hello World!</h1> ;
}
}
3. What is JSX?
JavaScript XML (JSX) is a popular syntax used to create UI components for JavaScript-based web applications. It allows you to create complex UIs by combining JavaScript and HTML.
JSX produces DOM elements, which makes it very useful for creating HTML components. The benefit of using JSX over just using HTML is that you have one source of truth for your component’s data and its presentation.
You can see an example of this in the following code snippet:
const root = <div>This is my root element</div>;
JSX works by taking a string of XML-like markup and converting it into an actual DOM element object. This process is known as "transpiling".
The JSX syntax looks like HTML mixed with JavaScript variables and other expressions. In fact, it's possible to use any valid JavaScript expression within your JSX code. See the example below:
const App = () => {
const name = "Ramotion";
return (
<h1>{name.toUpperCase()} is a design agency.</h1>
);
}
4. What is the virtual DOM?
Virtual DOM is an in-memory representation of the real DOM. It is useful for manipulating the real DOM efficiently and synchronously. Virtual DOM is independent of any JavaScript library or framework, but React uses it to power its declarative user interface (UI) model.
The virtual DOM is a JavaScript object tree that React uses to compare with the real DOM. The comparison determines which parts of the page need to be updated and what new content needs to be added.
The idea behind this approach is that instead of directly manipulating the DOM, we create and manipulate a lightweight representation of it. This allows us to compute and cache these changes before applying them to the real DOM, which makes our applications much more efficient.
5. What are synthetic events in React?
Synthetic events are used in React to create custom event listeners. These listeners will trigger when a particular event occurs. Synthetic events can be used to create custom behavior that can’t be handled by the browser natively.
What are the advantages of using synthetic events in React?
- Synthetic events are easier to manage than browser’s native events. This is because they can be used to create custom listeners that will trigger when a particular event occurs, without having to wait for browser support.
- Synthetic events can be used to create custom behavior that can’t be handled by the browser natively.
For example:
import React from 'react';
class MyButton extends React.Component {
toggleClicked() {
console.log('The button was clicked');
}
}
render() {
return (
<button onClick={this.toggleClicked}>Click me</button>
);
}
6. What is React Fiber?
React Fiber is a reimplementation of React's core algorithm. It makes incremental changes to a running application and provides an API for asynchronous rendering and other patterns.
The goal of this project is to make components more efficient so that we can achieve better rendering performance and smoother user experience on large data sets. This will be accomplished by introducing a parallel execution model, where updates are batched together before being applied to the DOM. We also want to make it easier for users to reason about their applications by making performance predictable and consistent even when faced with complicated data hierarchies or complex interactions between components.
7. What are the different phases of the component lifecycle?
A React component has lifecycle methods that are called at different points of its life. These methods are used to perform certain actions during the lifetime of a component.
There are three phases in total:
Mounting
The component is initialized and mounted to the DOM. This is where you should be doing your initial data fetching, and anything else that needs to happen before the component has been rendered for the first time.
Updating
This is the phase in which you should be doing any asynchronous data updates to your component. Components are immutable by default, and so this is where you can mutate state without worrying about side effects. As a rule of thumb, if your component has an attribute called “state” or “props”, then you should use these instead of modifying the component directly.
Unmounting
This is the phase where you should be doing any cleanup, validation, and/or data saving that needs to happen before your component has been removed from the DOM. You can use this as an opportunity to clean up any subscriptions or event listeners that were registered while it was mounted.
8. What are the lifecycle methods of React?
componentWillUnmount()
This method gets called before any other react component’s lifecycle method, and it's useful for initializing things that don't need to be done at render time, such as starting up a WebSocket connection or making an AJAX request. It also lets you know when your component will mount so you can do things like set up event handlers/ listeners or load data if necessary.
componentWillMount()
This method gets called before render, but after the component is created and attached to the DOM. You can use it to set up event listeners or load data if necessary. It’s useful for initializing things that don’t need to be done at render time, such as starting up a WebSocket connection or making an AJAX request.
componentDidMount()
This method gets called after the component has fully rendered and updated its DOM node with its markup. This is an ideal place to make server requests or perform other actions that need to happen after the initial render completes.
getDerivedStateFromProps()
This method is called when props change and can be used to update the component’s state. The default implementation returns null. If your component needs to keep track of something that depends on props, you should override this method with your own version that uses React’s setState() function to update the component’s internal data structures.
shouldComponentUpdate()
This method is used to determine if a component needs to re-render when its props or state change. The default implementation returns false, but you can override this method with your own version that determines if a re-render should occur. You should only do this when the data structure itself has changed and not just the values of individual items in that structure! For example, if an array of objects is passed as props and one of those objects changes, it is not necessary for all of them to be re-rendered since each object’s data remains unchanged.
getSnapshotBeforeUpdate()
This method is used to get a snapshot of the component’s current state before it is updated. The default implementation returns null, but you can override this method with your own version that determines if a snapshot should be taken and what data should be included in that snapshot. After all props and state updates have been made, React will call this method on the next frame (via requestAnimationFrame) so that any effects from those updates can take place.
9. What are stateless components?
Stateless components are very similar to presentational (dumb) components, however, they don’t have any state. They don’t know anything about the data they display or how it changes over time. Instead, they just pass down props to their children which contain all the information required for rendering a particular part of the UI.
The benefit of this approach is that we can easily reuse our stateless components in other parts of our application without worrying about them being affected by any other part of our codebase. Stateless components also make it easier to unit test individual UI elements without having to worry about their dependencies on other parts of the app.
A component is stateless if the only way to change the output of its render method is by updating the props passed to it. It's important to note that a stateless component can still have an internal state, but this state has no effect on the rendered result. In other words, a stateless component never requires an instanceof key or needs to pass a function down in order to properly initialize it.
10. What are stateful components?
Stateful components are a way to manage the state in React. With the help of this concept, we can separate our application into separate parts that each manage their own state. This makes our applications easier to reason about and test.
The state is any information that can be used to change the output of a component. For example, if you have a button that changes color when it's clicked, the color state. If you have an object that tracks whether or not something has been purchased, that object is also state.
Stateful components have their state stored in a separate object. This can be accessed through the this.state property and is often initialized with an initial value.
11. What is the strict mode in React?
Strict mode is a way to make React more strict in how it behaves. It allows you to catch common mistakes and fix them before they cause problems.
There are a few things that make strict mode unique.
- First, it's an opt-in feature. This means that you need to explicitly add the "use strict"; directive at the top of your JavaScript file to enable strict mode.
- Second, you can use strict mode in both browser and Node.js environments. The way you use it is different, but the same concepts apply.
- Third, strict mode evaluates all your code as strict by default until you tell it otherwise by adding "use strict"; at the beginning of your file. This makes sure that any errors or warnings will be caught immediately instead of waiting until runtime.
This is how you initialize strict mode in React:
// index.js
root.render(
<React.StrictMode>
<App />
</React.StrictMode>
);
12. What are Props?
Prop is short for Property. It's a way to pass data from parent to child components. Component props are used to transfer data from parent to child elements in React. A parent element can pass values down to its children using props.
Props are a great way for you to pass data from the top of your application down through its layers to your individual UI components. Props are always immutable and should be used as an alternative to state (state is mutable and should only be used at the top level).
Example:
function Todo(props) {
return (
<div>
<h1>{props.name}</h1>
<p>{props.time}</p>
</div>
)
}
function App() {
return (
<Todo name={"Write 100 words"} time={"30 minutes"} />
);
}
See in the above code snippet we are able to pass data (name and time) from the parent component (App) to the child component (Todo).
13. What is Redux?
Redux is a predictable state container for JavaScript apps. It helps you write applications that behave consistently, run in different environments (client, server, and native), and are easy to test. On top of that, it provides a great developer experience, such as live code editing combined with a time-traveling debugger.
Redux is not a framework. It doesn’t dictate how you organize your application or where to put things. Instead, it provides a few simple rules that help you implement an architecture that makes sense for the way you write applications.
By using Redux you can create complex applications that behave consistently and more importantly, you can easily test them.
Redux uses the following principles:
- Single source of truth - The entire state of your app is stored in an object tree inside a single store. This allows you to evaluate the current state of your application by simply looking at this store's state at any point in time.
- State is read-only - The only way to change the state is to emit an action, an object describing what happened. To trigger an update, you dispatch an action, which causes the reducer function to be called with the current state and your payload as arguments, returning a new state value. That new state value is then applied to the view layer.
- The state can only be mutated by pure functions - The only way to mutate the state is by emitting an action which is a plain JavaScript object. These actions are dispatched to the store, where they're processed by reducers that modify the application's state.
14. What are Hooks in React?
Hooks are a new feature of the React JavaScript library. They're specifically designed for components, but can also be used for stateless functional components that don't use classes.
The React Hooks API has been designed to be more flexible than higher-order components (HOCs) while maintaining the same level of code reuse as class-based components (BCCs). The goal is to make it easier to write code that's more readable and understandable, while also enabling new patterns such as stateful/stateless functional components without having to resort to HOCs or ES6 classes.
The main reason why React introduced Hooks was that developers found it hard to manage the state when they used class-based components. If you were using class-based components, then you had no choice but to use setState() or componentWillMount(). You could also use componentDidMount() if you wanted an initial value for your component's state. These methods were not very flexible because they couldn't be used everywhere. For example, you couldn't use them inside loops or nested functions inside your component's render() method.
With Hooks, you can easily solve this problem by creating a function instead of using setState(). You can pass down data from one component to another using React context or simply share data with multiple components at once by passing down it as a prop.
The below code snippet shows how to use the useState() hook to update state:
import React, { useState } from "react";
function App() {
const [claps, setClaps] = useState(0);
function incrementClaps() {
// adding 1 to the previous claps count every time the "Clap" button is clicked
setClaps(claps + 1);
}
return (
<div>
<h1>{claps}</h1>
<button onClick={incrementClaps}>Clap</button>
</div>
)
}
15. What are Custom Hooks?
Custom Hooks in React is a way to use functions to extend the React API. This allows you to add new functionality to your components while keeping them small and reusable.
16. What is React Router?
React Router is a library for navigating views in React applications. It's the standard navigation solution for React apps.
Routing determines what content to render based on the URL. For example, if you have a blog, then you might want to display blog posts when someone visits /blogs/{id}.html. You can use React Router to render different components depending on the URL (e.g., /blog/:id).
React Router is one of the most popular libraries for React. It provides a simple, declarative API that makes it easy to understand how the application will react when navigating between pages. The library uses history and location APIs provided by browsers, which means that you don’t have to worry about cross-browser compatibility issues.
The key features of React Router are:
- Routing should be declarative and predictable.
- Strict mode is opt-in and will help you avoid common mistakes with URL handling.
- Routes can be nested and composed using children.
- Route parameters are supported.
- Route names are supported, which makes it easy to highlight or update links from other parts of your application without changing any of the existing routing configurations.
To get started, install react-router with NPM:
npm install react-router react-router-dom
Use it like this:
// index.js
import React from "react";
import ReactDOM from "react-dom/client";
import {
createBrowserRouter,
RouterProvider,
Route,
} from "react-router-dom";
import "./index.css";
const router = createBrowserRouter([
{
path: "/",
element: <div>Hello world!</div>,
},
{
path: "/about",
element: <div>About Me</div>,
},
]);
ReactDOM.createRoot(document.getElementById("root")).render(
<React.StrictMode>
<RouterProvider router={router} />
</React.StrictMode>
);
17. What is Jest?
Jest is an open-source JavaScript testing platform created by Facebook, inspired by Jasmine and other existing frameworks. It provides a stable API to write tests for your code, along with a set of plugins that help you test the most common things.
It also provides a lot of helpful features, like mocking, code coverage, and snapshot testing. You can use it to write your unit tests, as well as your end-to-end tests. This makes testing your JavaScript code a breeze, and you can use it in both Node.js projects as well as React apps.
The core feature of Jest is snapshot testing. Snapshots are time-traveling data comparisons that tell you what changed between two different states of your codebase. They're typically used to test React components, but can be used for other things as well.
If you're new to testing, Jest makes it easy to start with a "zero configuration" approach. If you're already using Karma or Mocha, you can use Jest as a drop-in replacement for your current test runner.
18. What is Flux
Flux is a popular design pattern that can be used in React applications to manage state. It's a simple concept: when an application emits a change event, any components listening to it can update their local state.
This makes it possible to create reusable components that don't have to know about the entire application's state. A component can be rendered multiple times, each time using the most recent version of its own local state.
Flux relies on three basic building blocks:
- Store - A store manages the application's data and is usually responsible for managing information from multiple sources. A store can contain several subcomponents called "reducers" that determine how changes are applied to its state based on incoming actions from other parts of the system.
- Action - Actions are objects that describe what happened in the application. They usually contain information about the type of action, any relevant data, and a function that is called when the action is received by the store. You can think about actions as react events that trigger updates in your application's state.
- Views - Views are used to display your application's UI. They usually receive data from stores and pass this information on to components that render HTML or JavaScript.
19. What are React Dev Tools?
React Developer Tools is a browser extension that allows you to inspect the React component hierarchy in the browser Developer Tools (DevTools). It also lets you view the component's props and state at runtime, as well as its child components.
20. What is render hijacking in react?
Render Hijacking is a technique that can be used to take over the output of other components. This is done by using the render prop pattern, which allows you to specify what the output of another component should be.
The easiest way to render hijack a component is by creating a custom element and using its render function as an input parameter for another component's children function. This will cause all of the child elements in the parent component's DOM tree that are passed through this parameter to be rendered by our custom element instead of the default rendering methods provided by React Native's built-in components.
21. What is React memo function?
React memo function is an important tool for the React developer to keep in mind when designing their application. It allows you to cache a component's output and reuse it later on, without having to recalculate the component every time.
So what does this mean? Let's say there is a component that takes a number and returns the square of that number. If I have a button that calls this component and sets some number on it, the user clicks on it and the number gets changed, the component will be re-calculated because we don't have anything cached yet. However, if we use memo(), we can cache what was returned from this function and use that same result again without re-calculating it, again and again, every time we click on our button!
You may need this if you have a lot of expensive operations that take up a lot of memory, like rendering or other expensive operations.
22. What is code-splitting?
The code we write is often made up of different components, each of which has its own component logic, styles, and dependencies. The problem with bundling all of these together into one file is that you end up downloading more code than you need at any given time. This results in larger file sizes, slower download times, and increased memory usage when the browser needs to parse everything at once.
Code-splitting in React is the process of splitting out components and their code into multiple files. This helps reduce the initial payload size and improves performance.
Code-splitting works by creating multiple bundles and loading them on demand. The main bundle is called the app bundle, or entry point, and all other bundles are called chunk bundles or lazy loaded bundles. Each chunk bundle contains only a portion of your application's code that's needed at run-time and can be loaded on demand when it becomes necessary.
23. What is React lazy function?
The React.lazy() function allows you to render a dynamic import as if it were a normal component, making the process of building components that are loaded dynamically yet rendered as regular components simple.
Example:
import React from "react";
import {
BrowserRouter as Router,
Routes,
Route
} from 'react-router-dom';
const Home = React.lazy(() => import('./pages/Home'));
const About = React.lazy(() => import('./pages/About'));
const Contact = React.lazy(() => import('./pages/Contact'));
function App() {
return (
<Router>
<Routes>
<Route path="/" element={<Home />} />
<Route path="/about" element={<About />} />
<Route path="/contact" element={<Contact />} />
</Router>
</Router>
);
}
24. What is NextJS?
Next.js is a framework that makes it easy to create server-rendered (SSR) and universal JavaScript applications. It's minimalistic, flexible, and extensible.
Next is a framework for Universal JavaScript apps. Universal means that the code you write runs on both the client (browser) and the server (Node). This makes it possible to share code between the two environments (for example your Redux store), which results in smaller payloads when loading your pages.
The second big feature of NextJS is "server-side rendering". Server-side rendering (SSR) is an approach to web application development where initial HTML pages are created before being sent to the browser for further processing/rendering by executing a script on the server side before sending them back to the browser for display or interaction by end users.
25. How JSX prevents Injection Attacks?
Injection attacks are a common way to compromise websites. They work by injecting malicious code into the source code of a website. For example, an attacker could inject some JavaScript that would execute in the browser and try to steal user credentials.
React DOM automatically converts any values embedded in JSX before rendering them. It ensures that users can never inject anything into their application that isn’t explicitly written there -everything is converted to a string before being rendered.
26. What is diffing algorithm?
In React, the diffing algorithm is called the virtual DOM. It's a way of comparing two versions of your data and figuring out what has changed. This process is called diffing.
The diffing algorithm is at the heart of what makes React so powerful. It allows you to build your application using a declarative approach, without having to worry about the nitty-gritty details of how it will render on the screen.
27. How to Use CSS in React?
There are three ways to use CSS in React:
1. Using inline styles
Inline styles are the easiest way to use CSS with React. In-line styles are always used when you want to style a particular element. However, the problem with inline styles is that they can be hard to maintain as your app grows. Also, it’s not recommended to use them because they are harder to scale than external stylesheets.
import React from "react";
function App() {
return (
<div>
<h1 style={{ color: "green" }}>My App</h1>
</div>
);
}
2. Using external style sheets
External stylesheets are the most common way to use CSS with React. This approach allows you to separate your styling code from your application logic, which makes it easier to maintain and scale your app over time.
/* App.css */
.heading {
color: "green";
}
import React from "react";
import "./App.css";
function App() {
return (
<div>
<h1 className="heading">My App</h1>
</div>
);
}
3. Using third-party UI libraries
There are a lot of third-party UI libraries that can help you use CSS with React. These libraries usually provide a set of components and styles, which makes it easier to style your app without having to write all the code yourself.
Some popular third-party UI libraries for React:
28. What is prop drilling in React?
In React, prop drilling is the process of passing down props from parent components to their children. This allows us to build reusable components that can be easily customized by specifying different properties at different levels in our application tree.
29. What is context?
Context is a way of passing data through the component tree without having to pass props down manually at every level. It's often easier to think about it as a way to pass data from parent components to children.
Context is not a hard concept to understand, but it can be tricky to use in practice. It’s easy to misuse or overuse context, and it can be frustrating if you don’t know what it does and when it should be used.
Here's an example of a Context API:
import React from "react";
const TodoList = React.createContext(defaultValue);
class TodoList extends React.Component {
render() {
return <div>{this.props.todos}</div>;
}
30. What are the limitations of React?
React has some limitations that you should be aware of. First, it is not a complete framework by itself. It only handles the view layer and does not provide any features for routing or state management (though many frameworks have incorporated React into their stack).
Because of the way React was designed (as just a view layer), it doesn't really handle state management well at all. If you want to be able to store data about individual components and pass it around between them (e.g., save data from one form field into another), then you need to create your own state management system using Flux or Redux (see below).
React is not very good at handling DOM manipulation. It has a difficult time dealing with updates to the DOM that need to be made in response to user input or other events. This is one reason why React can feel "janky" at times because it's so easy for your app's UI
The learning curve is quite steep. It's not a framework that you can just dive right into without any prior knowledge of JavaScript or front-end development. If you want to use React effectively, then you'll need to learn how it works and how to use it properly first.
31. What are the key differences between ReactJS and AngularJS?
ReactJS is a JavaScript library for building user interfaces. It was developed by Facebook and released in 2013. ReactJS uses a component-based architecture which makes it very easy to integrate with other libraries or frameworks. It is one of the most popular front-end frameworks available today.
AngularJS is a JavaScript framework developed by Google. It uses MVC (Model View Controller) architecture to create web applications. AngularJS helps developers to write less code and make their applications more responsive and flexible. Both ReactJS and AngularJS are popular among developers as they allow fast development of user interfaces that are highly responsive.
AngularJS uses HTML markup with custom tags such as ng-repeat and ng-view while ReactJS uses HTML markup only with virtual DOM diffing algorithm which updates only those parts of the DOM which actually change instead of updating the whole page whenever there is a change in any part of DOM (Document Object Model). This makes rendering very fast as well as decreases bandwidth usage when compared with other frameworks like AngularJS where the entire page gets rendered every time even if only a small part of it has changed.
It's one of the biggest differences between these two frameworks when it comes to state management. In ReactJS, the state is managed by the developer themselves, while in AngularJS it's managed by the framework itself.
Another difference between React and Angular is in the way they approach writing code. Angular uses two-way data binding, which means that any change that happens on one side of the application immediately propagates to other parts of the app as well. In React, every time you make an update, there will be an asynchronous process involved before the data starts flowing again. This makes Angular much slower than React when there are large amounts of data being processed at one time.
Conclusion
React is a library for creating complex user interfaces for web and mobile applications. Think about it as the V in MVC. It helps you create reusable ui components. React is fast, intuitive, and flexible. There's been a lot of debate about the usefulness of React but we believe that it's best to know about it as well as to know why there's a debate around it. These questions will give helps you learn about the library as well as about why people call it overrated or under-rated.
Hopefully, this has given you a couple of better insights into what you can expect in a React interview and some ideas on how to prepare for the time when that interview comes around. You're now ready to ace any React interview!