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3,048 react developer interview questions shared by candidates

Mobile application development: - What development platform do you recommend for mobile app? - How do you minimize security risks? - You’ve just been alerted that your new app is prone to crashing. What do you do? [How do you troubleshoot a crashing application?] - Which JSON framework is supported by iOS? - What are the best ways of achieving concurrency in iOS? - What are the new feature in Swift 5.0?: Just give 1-2 features, there are major updates in swift 5.0 - What mechanism does iOS support for multi-threading? - Provide some tips to reduce battery usage in an mobile application React native: - What is your fav hook, how to implement it. - List some benefits of using React Native for building mobile apps? - Can we combine android and ios code in react native? - What is difference between state and props? - What are components of react native?
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Senior React Developer

Interviewed at HashTrust Technologies

4.8★
Jun 24, 2021

Mobile application development: - What development platform do you recommend for mobile app? - How do you minimize security risks? - You’ve just been alerted that your new app is prone to crashing. What do you do? [How do you troubleshoot a crashing application?] - Which JSON framework is supported by iOS? - What are the best ways of achieving concurrency in iOS? - What are the new feature in Swift 5.0?: Just give 1-2 features, there are major updates in swift 5.0 - What mechanism does iOS support for multi-threading? - Provide some tips to reduce battery usage in an mobile application React native: - What is your fav hook, how to implement it. - List some benefits of using React Native for building mobile apps? - Can we combine android and ios code in react native? - What is difference between state and props? - What are components of react native?

Diff btwn functional and class based component, how can we replicate lifecycle method in functional , component, js questions like closure, hoisting, let var, const , coding question to remove duplicates from given , also asked me to create a react form with validation , intrview duration 45 mins .
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React Js Developer

Interviewed at Cognizant

3.5★
Mar 22, 2025

Diff btwn functional and class based component, how can we replicate lifecycle method in functional , component, js questions like closure, hoisting, let var, const , coding question to remove duplicates from given , also asked me to create a react form with validation , intrview duration 45 mins .

Round 1: Frontend (Machine Coding - React) The interviewer asked me to develop a file system in React. It was a machine coding round, and the interviewer was quite impressed with my solution. Round 2: Backend (System Design & JavaScript) This round focused on backend concepts. The interviewer asked: "What is the use of an API Gateway?" "Implement Promise.race() in JavaScript." A simple DSA question related to flight management (very easy level). "What is the purpose of CORS errors, and why don’t we get them in Postman?" Round 3: Java & Spring Boot This round tested my knowledge of Java and Spring Boot: "Why is dependency injection needed, and what is its purpose?" A simple DSA question: "Return the K greatest numbers from an array." "What are different HTTP status codes, and when are they used?" Round 4: Advanced Frontend (Rejection Round) Since I mentioned being strong in frontend, they gave me a challenging task: Implement API retries: If an API call fails, retry it 3 times with a 1-second delay. (My solution wasn’t perfect.) Build a product listing page with: Pagination Filtering Search functionality (by product name) Good CSS styling Time given: 40 minutes (I managed pagination and sorting but had bugs. Realistically, this would take 50-60 minutes in React.) Round 5: Project Deep Dive & Problem-Solving (Formality Round) This was more of a discussion round: Explained my project implementation in detail. "How is a HashSet implemented in Java?" Puzzle: "You have two ropes, each taking 30 minutes to burn. How do you measure exactly 45 minutes? (You can’t bend them or measure half accurately.)" My answer: Burn one rope from one end (30 mins) and the other from both ends (15 mins). Total = 45 mins. The interviewer was satisfied. They deep-dived into my projects to assess my understanding.
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Java react fullstack developer ICT3 role

Interviewed at Apple

4.1★
Apr 8, 2025

Round 1: Frontend (Machine Coding - React) The interviewer asked me to develop a file system in React. It was a machine coding round, and the interviewer was quite impressed with my solution. Round 2: Backend (System Design & JavaScript) This round focused on backend concepts. The interviewer asked: "What is the use of an API Gateway?" "Implement Promise.race() in JavaScript." A simple DSA question related to flight management (very easy level). "What is the purpose of CORS errors, and why don’t we get them in Postman?" Round 3: Java & Spring Boot This round tested my knowledge of Java and Spring Boot: "Why is dependency injection needed, and what is its purpose?" A simple DSA question: "Return the K greatest numbers from an array." "What are different HTTP status codes, and when are they used?" Round 4: Advanced Frontend (Rejection Round) Since I mentioned being strong in frontend, they gave me a challenging task: Implement API retries: If an API call fails, retry it 3 times with a 1-second delay. (My solution wasn’t perfect.) Build a product listing page with: Pagination Filtering Search functionality (by product name) Good CSS styling Time given: 40 minutes (I managed pagination and sorting but had bugs. Realistically, this would take 50-60 minutes in React.) Round 5: Project Deep Dive & Problem-Solving (Formality Round) This was more of a discussion round: Explained my project implementation in detail. "How is a HashSet implemented in Java?" Puzzle: "You have two ropes, each taking 30 minutes to burn. How do you measure exactly 45 minutes? (You can’t bend them or measure half accurately.)" My answer: Burn one rope from one end (30 mins) and the other from both ends (15 mins). Total = 45 mins. The interviewer was satisfied. They deep-dived into my projects to assess my understanding.

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