Wissen Infotech React Developer Interview Questions and Answers

There was a test with JS and React MCQs. Plus subjective questions which are these.
1. Write a function that keep track of how many times it is called
2. What are Sass, Less, Postcss and Stylus? Why do people use them?
3. What is CSS flexbox? Explain with a simple example.
4. What is the difference between RequireJS, CommonJS and AMD Loaders?
5. Write a function that flattens an array of nested arrays into a single array.
6. What is Callback Hell? How do you avoid it?

Q1. What is React? Why do we use it? Make a form with 3 different child components and pass props from the parent. There should be Select box, an Input field and a Submit Button.
Ans. 
React is a JavaScript library used for building user interfaces.
• React allows for reusable components and efficient rendering.

• It uses a virtual DOM to update only the necessary parts of the UI.

• React is popular for its simplicity and flexibility.

• Examples of companies using React include Facebook, Instagram, and Airbnb.
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Q2. What is Virtual DOM?
Ans. 
Virtual DOM is a lightweight copy of the actual DOM that React uses to update the UI efficiently.
• Virtual DOM is a JavaScript object that represents the actual DOM.

• It allows React to update only the necessary parts of the UI, improving performance.

• Changes made to the Virtual DOM are compared with the previous version to determine the minimum number of changes needed to update the actual DOM.

• React uses a diffing algorith...read more
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Q1. Questions about project, experience etc.
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