Here, we have assembled the list of top 30 ReactJS interview questions & answers for freshers & experienced candidates.
In the fast-evolving world of web development, ReactJS stands out as a game-changer. Powering applications like Facebook and Instagram, this JavaScript library has become the go-to tool for creating dynamic, high-performance user interfaces. Whether you’re a beginner stepping into the tech world or a seasoned developer aiming to stay ahead, mastering ReactJS is essential.
To help you shine in your next interview, we’ve put together an engaging list of the top 30 ReactJS interview questions and answers. From fundamental concepts to advanced techniques, this guide has everything you need to confidently demonstrate your expertise and impress your interviewer. Let’s dive in and prepare to ace your ReactJS journey!
ReactJS Interview Questions & Answers:
- Define ReactJS?
ReactJs or React is an open-source front-end development JavaScript library developed by Facebook. It is used in their products like Facebook, WhatsApp, and Instagram. Facebook originally maintained it, but afterward, it was made open-source and now has a lively developer community. React allows developers to create reusable UI components that manage their state, making the development process efficient and modular.
2. Tell me some features of ReactJs?
Some of them are:
- React increases efficiency
- React improves SEO performance
- React ensures stable code
- React makes the process of writing components easier
3. How ReactJs framework is different as compared to others?
ReactJS is a library focused on building user interfaces, unlike frameworks like AngularJS that provide complete solutions for building applications, including state management and routing.
4.What are the lifecycles of ReactJs?
The ReactJS Lifecycles refers to the series of events that occur from their creation to their removal from the DOM. The React lifecycle is generally divided into three main phases:
- Mounting: This phase begins when a component is created and inserted into the DOM.
- Updating: This phase occurs when a component’s state or props change, leading to re-rendering.
- Unmounting: This phase happens when a component is removed from the DOM.
5. When ReactJs released?
March 2013
6. Define Redux?
It is one of the most in-insist libraries for front-end expansion in today’s growing world. It is defined as the unsurprising state container mainly intended for JavaScript apps, and also it is used for the organization the whole state of an application. Redux is very diminutive in size and has no dependencies. It builds applications that are simple to arrange in diverse environments and easy to test. Redux is very small in size and has no dependencies.
7. Tell me the use of Redux Thunk?
Redux Thunk acts as middleware which permits an individual to mark action creators that return functions in its place of actions. This is also used as a holdup function in order to wait for dispatch of an effort if a convinced condition is met. The two store methods gestate (), and dispatch () are provided as parameters to the inside function.
8. What is Flux?
Flux is an essential picture that is obliging in maintaining the unidirectional data stream. It is meant to control construed data sole fragments to make the border with that data without creating issues. Flux pattern is insipid; it’s not detailed to react applications, nor is it obligatory to collect a React application. Flux is an uncomplicated idea; however, you have to reveal a reflective comprehension of its usage.
9. What is the repository URL of ReactJs?
https://github.com/facebook/react
10. Do you think ReactJS has any limitations?
Yes, there are a few difficulties which are linked with this platform. The foremost drawback of the ReactJs is the dimension of its library. It is very multifaceted and creates a lot of perplexity amongst the developers. Also, there are lots of developers who don’t like the JSX and inline templating.
11. What is a state in React and how is it used?
In React, State is a thing that represents how the part renders and behaves. States are the sources of data and permit you to generate dynamic and interactive components. They are accessed using this. state(). For altering a value in the state object, call it using this.setState() method.
12. What are the limitations of React?
Limitations of React are listed below:
- Its library is very large and takes time to understand
- Coding gets complex as it uses inline tempting and JSX
- It can be a little difficult for novice programmers to understand
- React is just a library, not a full-blown framework
13. Why can’t browser’s 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.
14. List some of the cases when you should use Refs?
Refs. Should be used:
- To trigger imperative animations
- Integrate with third-party DOM libraries
- When you need to manage focus, select text or media playback
15. Tell us the reason behind the success of ReactJs?
React JS is a technology that can be credible for complex tasks. While performing any task through it, developers need not be worried about the bugs. It always ensures error-free outcomes and the best part is it offers scalable apps.
16. What is react-router?
Reading the components is an important task in React JS. It is used to decide which components are to be rendered and which one should not.
17. What can you do with HOC?
HOC can be used for many tasks like:
- Render High Jacking
- Props Manipulation
- State abstraction and manipulation
- Code reuse, logic and bootstrap abstraction
18. What are the different types of components?
There are two types of components:
19. How to pass values as input to a component?
We can pass values by using props.
20. Name the different types of DOM?
The different types of DOM are:
21. Which function is used to create UI representation?
React.createElement()
22. What are high order components?
An upper order component is a purpose that takes a component and returns a new part.
23. Define portals in React?
Portal is an optional way to make children into a DOM node that exists exterior the DOM order of the parent component.
24. What are stateful components?
If the behaviour of a part is reliant on the state of the component, then it can be termed as a stateful component. These stateful components are forever class components and have a condition that gets customized in the constructor.
25. Define react DOM server?
The React DOM Server object allows us to make components to static markup. This object is typically used for server-side rendering. The below techniques can be used in both the server and browser environments:
- renderToString()
- renderToStaticMarkup()
26. What is the lifecycle methods order in mounting?
The lifecycle techniques are called in the under the order when an example of a component is being created and inserted into the DOM.
- constructor()
- static getDerivedStateFromProps()
- render()
- componentDidMount()
27. What is React Router?
React Router is a reliable routing library build on top of React that assists you add novel screens and flows to your application extremely quickly, all while keeping the URL in sync with what’s being displayed on the page.
28. Define Jest?
JavaScript unit testing structure created by Facebook based on Jasmine and provides mechanical mock creation and a jsdom setting. It’s often used for testing components.
29. What props are in React JS?
Props mean properties, it’s a method of passing data from father to child, and we can say that props are just a communication canal between components. Always moving from parent to child component. It’s immutable and read-only.
30. What is the super keyword in React?
The super keyword is used to admission & call functions on an object’s parent.
31. How to create an event in React?
class Display extends React.Component({
show(evt) {
// code
},
render() {
// Render the div with an onClick prop (value is a function)
return (
Download here
);
}
});
So, above are the following interview questions & answers for ReactJS jobs, candidates should go through it and search more to clear the job interview efficiently.
