Coding Questions
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You're reviewing code and notice a component that handles user preferences. What potential issue exists in this implementation?
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ReactCode reviewError handling+1
Easy
Your team is implementing a custom form validation library. Complete the missing code in this custom hook:
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ReactFormsValidation+2
Hard
A junior developer is building a todo list application and can't figure out why their delete functionality isn't working. What's the issue with the delete functionality, and how should it be fixed?
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ReactEventsScope+1
Easy
What is the output of the following asynchronous code?
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PromisesEvent loop
Hard
What is the difference between == and === in JavaScript?
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Type coercionJavascript
Easy
In a React application, you're building a dynamic list of thousands of clickable items. Each item needs to track when it's clicked. Which implementation would be most performance-efficient and why?
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ReactEvent delegationPerformance optimization+2
Medium
You're building a data grid component that needs to handle sorting, filtering, and pagination efficiently. What's missing in this implementation to make sorting work correctly?
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ReactSortingUsememo+1
Medium
Which of the following code snippets correctly implements the map method?
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ArraysMapPrototypes+1
Hard
You're implementing an auto-save feature for a document editor. During testing, you notice that the save function is being called too frequently during rapid typing. What's the best way to optimize this code?
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ReactDebounceThrottle+2
Medium
Which array method would you use to find the first user with an age greater than 30?
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ArraysIterationFind+3
Easy
You're debugging a performance issue in a React component. The team lead mentions that unnecessary re-renders might be the culprit. What's the problem in this code?
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ReactReact performanceMemoization+2
Easy
Which method would you use to merge two arrays without modifying either of them?
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ArraysConcatSpread operator
Easy
What does the following code log to the console?
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SetArraysJavascript
Easy
You're building a caching system that shouldn't prevent objects from being garbage collected. What's wrong with the current implementation and which solution properly handles memory management?
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JavascriptWeakrefGarbage collection+2
Hard
You're building a React component for a weather dashboard. Which implementation correctly updates the temperature display?
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ReactUsestateState updates+1
Easy