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/**
* Options for useDebounce hook
*/
export interface UseDebounceOptions {
/**
* Maximum time the debounced value can be delayed
* @default undefined (no maximum)
*/
maxWait?: number;
/**
* Whether to update the debounced value on the leading edge
* @default false
*/
leading?: boolean;
/**
* Whether to update the debounced value on the trailing edge
* @default true
*/
trailing?: boolean;
}
/**
* Debounces a value by delaying updates until after a specified delay period has elapsed
* since the last time the value changed. Useful for search inputs and API calls.
*
* @template T - The type of the value to debounce
* @param value - The value to debounce
* @param delay - The delay in milliseconds (default: 500ms)
* @param options - Additional options for controlling debounce behavior
* @returns The debounced value
*
* @example
* ```tsx
* function SearchInput() {
* const [searchTerm, setSearchTerm] = useState('');
* const debouncedSearchTerm = useDebounce(searchTerm, 500);
*
* useEffect(() => {
* if (debouncedSearchTerm) {
* // API call with debounced value
* searchAPI(debouncedSearchTerm);
* }
* }, [debouncedSearchTerm]);
*
* return (
* <input
* type="text"
* value={searchTerm}
* onChange={(e) => setSearchTerm(e.target.value)}
* placeholder="Search..."
* />
* );
* }
* ```
*
* @example
* ```tsx
* // With leading edge update
* const debouncedValue = useDebounce(value, 300, { leading: true });
* ```
*
* @example
* ```tsx
* // With maximum wait time
* const debouncedValue = useDebounce(value, 500, { maxWait: 2000 });
* ```
*/
export function useDebounce<T>(
value: T,
delay: number = 500,
options: UseDebounceOptions = {}
): T {
// Parse options
const wait = delay || 0;
const leading = options.leading ?? false;
const trailing = options.trailing !== undefined ? options.trailing : true;
const maxing = "maxWait" in options;
const maxWait = maxing ? Math.max(options.maxWait || 0, wait) : undefined;
const [debouncedValue, setDebouncedValue] = useState<T>(value);
const timerIdRef = useRef<ReturnType<typeof setTimeout> | undefined>(
undefined
);
const lastCallTimeRef = useRef<number | undefined>(undefined);
const lastInvokeTimeRef = useRef<number>(0);
const lastValueRef = useRef<T>(value);
const prevValueRef = useRef<T>(value); // Track previous value to detect actual changes
// Store options in refs so the timer callbacks always read the latest values.
// Initialised from the first render's options; kept in sync via the effect
// below (never mutated during render, to preserve render purity).
const waitRef = useRef(wait);
const leadingRef = useRef(leading);
const trailingRef = useRef(trailing);
const maxingRef = useRef(maxing);
const maxWaitRef = useRef(maxWait);
// Self-reference indirection for the recursively-restarting trailing timer.
const timerExpiredRef = useRef<() => void>(() => {});
// Helper: shouldInvoke — reads all mutable state through refs, so it can be a
// stable closure created once (no per-render reassignment).
const shouldInvoke = useCallback((time: number): boolean => {
const lastCallTime = lastCallTimeRef.current;
if (lastCallTime === undefined) {
return true; // First call
}
const timeSinceLastCall = time - lastCallTime;
const timeSinceLastInvoke = time - lastInvokeTimeRef.current;
return (
timeSinceLastCall >= waitRef.current ||
timeSinceLastCall < 0 || // System time went backwards
(maxingRef.current &&
timeSinceLastInvoke >= (maxWaitRef.current as number))
);
}, []);
// Helper: invokeFunc
const invoke = useCallback((time: number): void => {
setDebouncedValue(lastValueRef.current);
lastInvokeTimeRef.current = time;
}, []);
// Helper: remainingWait
const remainingWait = useCallback((time: number): number => {
const lastCallTime = lastCallTimeRef.current;
Iif (lastCallTime === undefined) {
return waitRef.current;
}
const timeSinceLastCall = time - lastCallTime;
const timeSinceLastInvoke = time - lastInvokeTimeRef.current;
const timeWaiting = waitRef.current - timeSinceLastCall;
return maxingRef.current
? Math.min(
timeWaiting,
(maxWaitRef.current as number) - timeSinceLastInvoke
)
: timeWaiting;
}, []);
// Helper: trailingEdge
const trailingEdge = useCallback(
(time: number): void => {
timerIdRef.current = undefined;
// Only invoke if we have `lastCallTimeRef.current`, which means `value`
// has been debounced at least once.
if (trailingRef.current && lastCallTimeRef.current !== undefined) {
invoke(time);
}
},
[invoke]
);
// Helper: timerExpired — self-restarts through timerExpiredRef.
const timerExpired = useCallback((): void => {
const time = Date.now();
if (shouldInvoke(time)) {
trailingEdge(time);
} else {
// Restart the timer.
timerIdRef.current = setTimeout(
() => timerExpiredRef.current(),
remainingWait(time)
);
}
}, [shouldInvoke, trailingEdge, remainingWait]);
// Helper: leadingEdge
const leadingEdge = useCallback(
(time: number): void => {
// Reset any `maxWait` timer.
lastInvokeTimeRef.current = time;
// Start the timer for the trailing edge.
timerIdRef.current = setTimeout(() => timerExpiredRef.current(), waitRef.current);
// Invoke the leading edge.
if (leadingRef.current) {
invoke(time);
}
},
[invoke]
);
// Sync option refs and the self-reference after commit — never during render.
// Declared before the main effect so the option refs are current by the time
// the value effect reads them within the same commit.
useEffect(() => {
waitRef.current = wait;
leadingRef.current = leading;
trailingRef.current = trailing;
maxingRef.current = maxing;
maxWaitRef.current = maxWait;
timerExpiredRef.current = timerExpired;
});
// Cleanup on unmount only
useEffect(() => {
return () => {
if (timerIdRef.current !== undefined) {
clearTimeout(timerIdRef.current);
}
};
}, []);
// Main debounce effect - runs when value changes
useEffect(() => {
// Skip if value hasn't actually changed (prevents initial render — and
// StrictMode's double-invoked mount effect — from consuming the leading edge)
if (Object.is(prevValueRef.current, value)) {
return;
}
prevValueRef.current = value;
const time = Date.now();
const isInvoking = shouldInvoke(time);
// Update lastValueRef with current value
lastValueRef.current = value;
lastCallTimeRef.current = time;
if (isInvoking) {
if (timerIdRef.current === undefined) {
leadingEdge(time);
E} else if (maxingRef.current) {
// Handle invocations in a tight loop.
clearTimeout(timerIdRef.current);
timerIdRef.current = setTimeout(() => timerExpiredRef.current(), waitRef.current);
// Only invoke if at least one edge is enabled (matches lodash behavior)
if (leadingRef.current || trailingRef.current) {
invoke(time);
}
}
} else {
if (timerIdRef.current === undefined) {
// Start timer with wait
// remainingWait is only used inside timerExpired for restarting
timerIdRef.current = setTimeout(() => timerExpiredRef.current(), waitRef.current);
}
}
// No cleanup here - timer should persist across value changes
// This is the key difference from the previous implementation
}, [value, shouldInvoke, leadingEdge, invoke]);
return debouncedValue;
}
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