Techweirdo Interview Questions and Answers

After resume screening, I was asked to create a data-driven form on a webpage using React and NodeJS.
A data-driven form is a kind of form where we do not hard code the fields(i.e. the data we want to gather by the form) we get the fields from the database instead.

Q1. What is multithreading in Javascript?
Ans. 
Multithreading is not natively supported in JavaScript, but can be achieved through Web Workers.
• JavaScript is a single-threaded language, meaning it can only execute one task at a time.

• Web Workers allow for multithreading in JavaScript by running scripts in the background.

• Web Workers can communicate with the main thread using message passing.

• Examples of tasks that can benefit from multithreading include heavy computati...read more
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Q2. A situation-based question on React.js regarding listing data on a page from an API.
Ans. 
Using React.js to fetch and display data from an API involves state management and lifecycle methods.
• Use the useEffect hook to fetch data when the component mounts.

• Utilize the useState hook to manage the fetched data.

• Handle loading and error states to improve user experience.

• Example: Fetching user data from an API and displaying it in a list.

• Consider using async/await for cleaner asynchronous code.
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Q3. Questions on setInterval() and setTimeout()
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Q4. Question on how DOM manipulation works in React.js
Ans. 
React.js uses a virtual DOM to optimize updates and improve performance during DOM manipulation.
• React creates a virtual DOM, a lightweight copy of the actual DOM.

• When state changes, React updates the virtual DOM first, not the real DOM.

• React uses a diffing algorithm to compare the virtual DOM with the real DOM.

• Only the changed elements are updated in the real DOM, minimizing performance costs.

• Example: If a list item is...read more
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Q5. What is virtual DOM?
Ans. 
Virtual DOM is a lightweight copy of the actual DOM used for efficient updates.
• Virtual DOM is a concept used in modern web development frameworks like React.

• It is a lightweight copy of the actual DOM that is used to track changes and update the actual DOM efficiently.

• When a change is made to the virtual DOM, it is compared with the previous version to identify the minimum number of changes required to update the actual...read more
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Q6. Easy questions on Node.js event loop.
Ans. 
The Node.js event loop manages asynchronous operations, allowing non-blocking execution of code in a single-threaded environment.
• The event loop is a core part of Node.js that handles asynchronous callbacks.

• It operates in phases: timers, I/O callbacks, idle, poll, check, and close callbacks.

• Example: setTimeout() schedules a callback to run after a specified delay.

• I/O operations (like reading files) are offloaded to the ...read more
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Q1. Basic questions on React.js and Node.js
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Q2. Also express.js was asked
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