JavaScript

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1. 01 Explain the JavaScript event loop, including microtasks vs macrotasks. Easy
2. 02 Predict the output order of a script mixing setTimeout, Promise.then, and synchronous code. Hard
3. 03 Explain closures with a practical example of a private counter. Easy
4. 04 Debug a classic closure-in-loop bug using var inside a setTimeout. Hard
5. 05 Explain the prototype chain and how it differs from classical inheritance. Easy
6. 06 Explain how Object.create and class syntax relate to prototypal inheritance under the hood. Hard
7. 07 Explain how Promises work internally, including states and the microtask queue. Easy
8. 08 Design error handling for a chain of dependent Promise.all calls where one branch is optional. Hard
9. 09 Explain how async/await desugars to Promises and generators. Easy
10. 10 Debug a case where awaiting inside a forEach loop doesn't work as expected. Hard
11. 11 Explain how the JavaScript engine allocates and manages memory. Easy
12. 12 Debug a growing heap size in a long-running SPA - what tools and steps do you use? Hard
13. 13 Explain the mark-and-sweep garbage collection algorithm. Easy
14. 14 Explain common causes of memory leaks in React apps (event listeners, closures, detached DOM nodes). Hard
15. 15 Explain WeakMap and why it helps prevent memory leaks compared to Map. Easy
16. 16 Design a caching layer using WeakMap keyed by DOM elements. Hard
17. 17 Explain WeakSet and a practical use case for tracking object state without leaks. Easy
18. 18 When would you choose WeakSet over a regular Set for tracking visited nodes? Hard
19. 19 Explain event delegation and why it's more performant for large lists. Easy
20. 20 Design an event delegation strategy for a virtualized list with 10,000 rows. Hard