JavaScript Interview Questions With AI-Powered Feedback

Frontend JavaScript interviews cover: the event loop and microtask queue, closures and scope, prototypal inheritance and the prototype chain, async patterns (Promises, async/await, Promise.all), var/let/const and the temporal dead zone, this binding and call/apply/bind, ES6+ features (destructuring, spread, generators, modules), and coding challenges like implementing debounce, throttle, deep clone, and curry.

The JavaScript event loop continuously checks the call stack and task queues. When the call stack is empty, it first processes all microtasks (Promise callbacks, queueMicrotask) before picking the next macrotask (setTimeout, setInterval, I/O). This means Promise .then() callbacks always run before setTimeout callbacks, even with a 0ms delay. Understanding this ordering is critical for frontend interviews.

A closure is a function that retains access to its outer scope's variables even after the outer function has returned. Closures are used for: data encapsulation and private variables, factory functions, memoization, event handlers that need access to loop variables, and implementing module-like patterns. Common interview questions ask you to implement debounce, throttle, or once() using closures.

Common JavaScript coding challenges include: implementing debounce and throttle, deep clone an object, flatten a nested array, implement Promise.all and Promise.race, curry a function, implement a simple event emitter, memoize a function, implement bind/call/apply, flatten an object, and implement a LRU cache. For frontend roles, challenges also include DOM manipulation and building small utilities.