useThrottle

Requirements

• Export useThrottle(value, interval) as a named and default React hook. Return the throttled value itself. In TypeScript preserve its type with useThrottle<T>(value: T, interval: number): T.
• interval is a finite positive number of milliseconds. Return the initial value immediately and begin an initial cooldown of interval milliseconds after mount. Invalid intervals are outside scope.
• During a cooldown, retain the published value and remember the latest input. At the cooldown deadline, publish that latest value if it differs by Object.is, and begin another cooldown from that publication.
• If the input has not changed by the deadline, end the cooldown without publishing. A later input change while idle publishes immediately after the effect and begins a new cooldown.
• Incoming values must not cancel or postpone a running cooldown. A sustained stream of changes therefore publishes at each cooldown deadline, always using the latest committed input.
• Changing interval cancels the pending timer and starts a fresh cooldown of the new duration, retaining the currently published value until its deadline. Changes with the same interval must not restart a timer.
• Preserve object and function identities, never invoking a function-valued input. Cancel pending timers on unmount, avoid duplicates in Strict Mode, and keep instances independent.
• Use real React state, effects, and refs. Exact millisecond execution follows browser scheduling. Fetch cancellation and callback throttling are outside scope.
• The supplied timer fixtures control setTimeout, clearTimeout, and Date.now to advance cooldowns deterministically; do not rely on real elapsed time in the tests.

Examples

Input: useThrottle("a", 100)
Output: Returns "a" immediately and begins a 100 ms cooldown.

Input: Input changes to "ab", then "abc" during that cooldown
Output: Keeps "a", then publishes "abc" at the deadline without extending it.

Input: After the cooldown ends without pending changes, input becomes "abcd"
Output: Publishes "abcd" after its effect and begins the next cooldown.