Premium

Debounce Function

By FrontendAtlas Team · Updated Feb 1, 2026

Implement debounce(fn, wait) that delays execution until the user stops triggering events. Clear the previous timer on each call, preserve this/args, and make the timing predictable for search/resize use cases.

What you’ll build / What this tests

This premium javascript coding focuses on Debounce Function. You’ll apply async and functions thinking with intermediate level constraints. The prompt emphasizes Implement debounce(fn, wait) that delays execution until the user stops triggering events. Clear the previous timer….

Learning goals

Translate the prompt into a clear javascript API signature and return shape.
Apply async, functions, timing techniques to implement debounce function.
Handle intermediate edge cases without sacrificing readability.
Reason about time/space complexity and trade-offs in javascript.

Key decisions to discuss

Define the exact input/output contract before coding.
Decide on concurrency and error propagation behavior.
Prioritize predictable edge-case handling over micro-optimizations.

Evaluation rubric

Correctness: covers required behaviors and edge cases.
Clarity: readable structure and predictable control flow.
Complexity: avoids unnecessary work for large inputs.
API discipline: no mutation of inputs; returns expected shape.
Testability: solution is easy to unit test.

Constraints / Requirements

Handle async flow without blocking the event loop.
Cancel stale work and only execute the latest call.
Return a Promise and resolve asynchronously without blocking.
Handle empty or missing inputs without throwing errors.
Keep runtime close to linear time where possible.
Prefer a pure function: no side effects beyond the return value.

Mini snippet (usage only)

// Example usage
const fn = /* debounce function input */;
const delay = /* config */;
const result = debounce(fn, delay);
console.log(result);

// Edge case check
const empty = fn && delay ?? null;
const fallback = debounce(fn, delay);
console.log(fallback);

// Expected: describe output shape, not the implementation
// (no solution code in preview)

Common pitfalls

Mutating inputs instead of returning a new value.
Skipping edge cases like empty input, duplicates, or nulls.
Forgetting to await or return the Promise.
Overlooking time complexity for large inputs.