Top 30 Basic React JS Interview Questions and Answers
July 12, 2021
logicrays
React is an efficient and declarative open-source JavaScript library. The front-end library was developed in 2011 by Facebook. React follows a component-based approach and builds reusable UI components. The library is used to creating single page application.
It helps to develop an interactive view layer for mobile and web apps. It was used to build Instagram & WhatsApp. Do you want to build a successful career in React JS?
Right now, React JS is one of the most popular front-end technologies which is being used by many companies. If you are going to appear in a job interview, then you should be aware of React JS interview questions and answers.
Having a comprehensive list of all the common React JS interview questions handy helps you to better understand the vital concepts of React JS.
Here are some React JS interview questions for experienced and beginners.
1. Explain features of React JS?
JSX: A JavaScript syntax extension that is used with React JS to describe the look of the UI.
Virtual DOM: React retains a lightweight representation of real DOM in memory known as virtual DOM.
Data binding – React JS provides one-way data binding that keeps everything fast and modular.
Components: These are the building blocks of React JS apps. An app consists of multiple components that split UI into reusable, independent parts that are separately processed.
2. Explain JSX?
JSX is an extension of JavaScript syntax. It is employed with React to define the UI. Using JSX helps to write HTML structures in a similar file as JavaScript code.
3.Can JSX be read directly by web browsers?
Web browsers do not directly read JSX. They are built to read regular JS objects. For a web browser to read a JSX file, the file should be transformed into a consistent JavaScript object.
4. Explain DOM?
DOM is Document Object Model. It represents an HTML document with a logical tree structure.
5. Why use React instead of other frameworks, like AngularJS?
Easy formation of dynamic apps
Better performance
Reusable components
Dedicated
Data flow
6. How do you create a React app?
Install NodeJS for npm to install React JS library
Need to Install the create-react-app package using command prompt
Install a text editor like VS Code
7. What is an event in React?
An event is one action that a user may trigger.
8. What is a higher-order component in React?
A higher-order component acts as a container for other components. It helps to keep components simple and enables re-usability. They are generally used when multiple components have to use a common logic.
The components of Redux are Store, Action, and Reducer.
11. What is React Router?
React Router is a routing library that is used to create routes in React apps.
12. What is the need for React Router?
– React Router maintains a consistent structure and is used for the creation of single-page web apps.
13. Explain the use of CSS modules in React.
The CSS module is available for the component which imported it, so that there is no naming conflict while styling components.
14. What are React props?
Props are short for Properties and are React built-in object which stores the attribute value of a tag.
15. What is a state in React?
A built-in React object is called a state and it is used to contain information or data about the component.
16. What is an arrow function?
A short way of writing a function to React is the arrow function.
17. How is the arrow function used in React?
Arrow function prevents the bugs that are caused by the use of ‘this’ in the React callbacks.
18. What are forms in React?
React uses forms to enable the users to interact with web applications.
19. Why is the need to use keys in Lists?
Keys are unique identifiers and it used to identify which are the changed items.
20. What are the synthetic events in React?
Synthetic events combine the native event of different browser’s responses into one API.
21. What are the advantages of React?
Below are the advantages of React:
Easy to learn and use
It becomes the creation of dynamic Web Apps easy
Reusable components
Enhances performance
It has the support of handy tools
It is SEO friendly
Provides the benefit of JavaScript Library
22. How can you update the component’s state?
The State of a component can be updated using this.setState() method.
23. How are the forms created in React?
In React, the state property of the component is updated via setState(), the submission is handled by a JavaScript function.
24. What are Pure Components?
Pure component improves the simplicity of code and improves the app’s performance.
25. What are Higher-Order Components (HOC)?
In React, HOC is an advanced technique that helps to reuse the component logic.
26. What can you do with HOC?
You can do the below tasks with HOC:
For reusability of Code
For manipulation of Props
Manipulation of state
For rendering high jacking
27. Why should we start component names with a capital letter?
In React, if the component name is starting with a lower case, then it throws an error as an unrecognized tag. In JSX, lower-case tag names get considered to be HTML tags.
28. What are fragments in React JS?
– In React, the Fragments are used for the components to return multiple elements.
29. What are refs in React?
Refs are the shorthand that is used for references in React. It helps to store a reference to a DOM node.
30. How to create refs?
Refs are created by using React. create Ref() and they are attached to React elements through the ref attribute.
So, cracking a React JS-based interview using react basic interview questions is a huge advantage. If you can crack advanced React JS interview questions, it provides wonderful career opportunities.
You can also look at React JS interview questions for 2 years of experience. The career also provides great pay for both beginners and experienced professionals. Below is the average salary for different profiles in India;
Frontend Developer – Rs 4,75,900
Backend Developer – Rs 6,80,700
Full Stack Developer – Rs 6,00,000
So do go through the above questions to ensure success in your interview and build a great career. Start learning React JS course from experts at Logicrays academy to get a 100% placement guarantee.
