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Throttle Function

By FrontendAtlas Team · Updated Feb 1, 2026

Implement a function throttle(fn, interval) that ensures fn is executed at most once during every interval milliseconds, no matter how many times it's triggered. In this exercise we use a leading-only throttle: the first call in each interval runs immediately; subsequent calls within that window…

What you’ll build / What this tests

This premium javascript coding focuses on Throttle Function. You’ll apply async and functions thinking with intermediate level constraints. The prompt emphasizes Implement a function throttle(fn, interval) that ensures fn is executed at most once during every interval….

Learning goals

Translate the prompt into a clear javascript API signature and return shape.
Apply async, functions, timing techniques to implement throttle 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.
Limit executions to a fixed interval and define trailing behavior.
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 = /* throttle function input */;
const interval = /* config */;
const result = throttle(fn, interval);
console.log(result);

// Edge case check
const empty = fn && interval ?? null;
const fallback = throttle(fn, interval);
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.