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useCallback,
useEffect,
useLayoutEffect,
useMemo,
useRef,
useState,
} from "react";
import type { KeyPressTarget, UseKeyPressOptions } from "./types";
import {
createMatcher,
isEditableElement,
isKeyPressSupported,
resolveTarget,
} from "./utils";
// SSR-safe layout effect: sync refs before paint on the client, fall back to
// useEffect on the server (mirrors the house useEventListener pattern).
const useIsomorphicLayoutEffect =
typeof window !== "undefined" ? useLayoutEffect : useEffect;
/** The four modifier flags tracked for a held trigger. */
type ModifierFlag = "ctrl" | "shift" | "alt" | "meta";
/**
* Maps a modifier key's `event.key` value to the {@link ModifierFlag} it toggles.
* Used on key-up to decide whether the released modifier was actually part of
* the held trigger (releasing an unrelated modifier must not end the press).
*/
const MODIFIER_KEY_TO_FLAG: Record<string, ModifierFlag> = {
Control: "ctrl",
Shift: "shift",
Alt: "alt",
Meta: "meta",
};
/**
* A React hook for detecting keyboard key presses, shortcuts, and combinations.
*
* Supports single keys (`"Escape"`), modifier combinations (`"mod+k"`,
* `"ctrl+shift+s"`), multiple alternative bindings (`["ctrl+s", "meta+s"]`),
* and custom predicates. The returned boolean reflects whether the target is
* currently pressed (with `eventType: "both"`, the default).
*
* Features:
* - Cross-platform `"mod"` alias (Ctrl on Windows/Linux, Cmd on macOS)
* - Exact or loose modifier matching
* - Match by logical key (`event.key`) or physical key (`event.code`)
* - `onPress` / `onRelease` callbacks with the raw event (for `preventDefault`)
* - Ignores auto-repeat and typing inside form fields (opt-in)
* - Resets on window blur to avoid stuck-key state
* - SSR compatible, with automatic listener cleanup
*
* @param target - The key(s) or predicate to detect. See {@link KeyPressTarget}.
* @param options - Configuration options. See {@link UseKeyPressOptions}.
* @returns `true` while the target key/combination is pressed.
*
* @example
* ```tsx
* // Single key state
* function Modal({ onClose }: { onClose: () => void }) {
* const escapePressed = useKeyPress("Escape");
* useEffect(() => {
* if (escapePressed) onClose();
* }, [escapePressed, onClose]);
* return <div>Press Escape to close</div>;
* }
* ```
*
* @example
* ```tsx
* // Cross-platform save shortcut with preventDefault
* function Editor({ onSave }: { onSave: () => void }) {
* useKeyPress(["ctrl+s", "meta+s"], {
* preventDefault: true,
* onPress: () => onSave(),
* });
* return <textarea />;
* }
* ```
*
* @example
* ```tsx
* // Command palette (mod = Ctrl on Win/Linux, Cmd on Mac)
* function App() {
* const [open, setOpen] = useState(false);
* useKeyPress("mod+k", {
* preventDefault: true,
* onPress: () => setOpen((prev) => !prev),
* });
* return open ? <CommandPalette /> : null;
* }
* ```
*
* @example
* ```tsx
* // Physical keys for game controls (layout-independent)
* function Game() {
* const forward = useKeyPress("w", { matchBy: "code" });
* const left = useKeyPress("a", { matchBy: "code" });
* return <Player moving={forward} turningLeft={left} />;
* }
* ```
*
* @example
* ```tsx
* // Predicate + scoped target
* function NumericField() {
* const ref = useRef<HTMLInputElement>(null);
* const digitPressed = useKeyPress((e) => /^[0-9]$/.test(e.key), {
* target: ref,
* });
* return <input ref={ref} data-active={digitPressed} />;
* }
* ```
*/
export function useKeyPress(
target: KeyPressTarget,
options: UseKeyPressOptions = {}
): boolean {
const {
target: eventTarget,
eventType = "both",
enabled = true,
preventDefault = false,
stopPropagation = false,
ignoreRepeat = true,
ignoreInputElements = false,
caseSensitive = false,
matchBy = "key",
exactModifiers = true,
onPress,
onRelease,
} = options;
const [pressed, setPressed] = useState(false);
// Mirror of `pressed` for synchronous reads inside event handlers.
const pressedRef = useRef(false);
// The lower-cased `event.key` that established the current pressed state.
const triggerKeyRef = useRef<string | null>(null);
// Snapshot of the modifier state at the moment the trigger keydown matched.
// Only modifiers that were held here should end the press when released.
const triggerModifiersRef = useRef<Record<ModifierFlag, boolean> | null>(null);
// Build the matcher once per distinct configuration. String/array targets are
// parsed here; function targets are used as-is.
const targetKey = typeof target === "function" ? target : JSON.stringify(target);
const matcher = useMemo(
() => createMatcher(target, matchBy, caseSensitive, exactModifiers),
// `targetKey` captures the serialized/string-or-function identity of `target`.
// eslint-disable-next-line react-hooks/exhaustive-deps
[targetKey, matchBy, caseSensitive, exactModifiers]
);
// Keep the latest reactive config in a ref so the attached listeners never go
// stale and never need to be re-registered when only callbacks/flags change.
const configRef = useRef({
matcher,
eventType,
preventDefault,
stopPropagation,
ignoreRepeat,
ignoreInputElements,
onPress,
onRelease,
});
// Sync the latest config in a layout effect (not during render) so we never
// mutate a ref while rendering — a render may be thrown away under concurrent
// rendering / StrictMode. Listeners read `configRef.current` at event time.
useIsomorphicLayoutEffect(() => {
configRef.current = {
matcher,
eventType,
preventDefault,
stopPropagation,
ignoreRepeat,
ignoreInputElements,
onPress,
onRelease,
};
}, [
matcher,
eventType,
preventDefault,
stopPropagation,
ignoreRepeat,
ignoreInputElements,
onPress,
onRelease,
]);
const setPressedState = useCallback((next: boolean) => {
pressedRef.current = next;
setPressed((prev) => (prev === next ? prev : next));
}, []);
// Clears any held state. When `releaseEvent` is supplied (window blur), fires
// `onRelease` so onPress/onRelease stay balanced; when omitted (disable /
// unsupported / unmount) it silently resets — see the onRelease JSDoc.
const resetPressed = useCallback(
(releaseEvent?: KeyboardEvent) => {
triggerKeyRef.current = null;
triggerModifiersRef.current = null;
if (pressedRef.current) {
setPressedState(false);
Eif (releaseEvent) {
configRef.current.onRelease?.(releaseEvent);
}
}
},
[setPressedState]
);
const handleKeyDown = useCallback(
(event: KeyboardEvent) => {
const config = configRef.current;
if (config.ignoreInputElements && isEditableElement(event.target)) {
return;
}
if (!config.matcher(event)) {
return;
}
if (config.preventDefault) {
event.preventDefault();
}
if (config.stopPropagation) {
event.stopPropagation();
}
const isSuppressedRepeat = event.repeat && config.ignoreRepeat;
if (!isSuppressedRepeat) {
config.onPress?.(event);
}
// In keyup-only mode the pressed state is driven by key releases.
Eif (config.eventType !== "keyup") {
triggerKeyRef.current = event.key.toLowerCase();
// Capture which modifiers were actually held when the trigger matched,
// so key-up can tell a bare-key press from a modifier combination.
triggerModifiersRef.current = {
ctrl: event.ctrlKey,
shift: event.shiftKey,
alt: event.altKey,
meta: event.metaKey,
};
setPressedState(true);
}
},
[setPressedState]
);
const handleKeyUp = useCallback(
(event: KeyboardEvent) => {
const config = configRef.current;
Iif (config.ignoreInputElements && isEditableElement(event.target)) {
return;
}
// keyup-only mode: a matching release latches the pressed state.
if (config.eventType === "keyup") {
Iif (!config.matcher(event)) {
return;
}
Iif (config.preventDefault) {
event.preventDefault();
}
Iif (config.stopPropagation) {
event.stopPropagation();
}
config.onRelease?.(event);
setPressedState(true);
return;
}
// "both" mode: release the held state when the primary key, or a modifier
// that was actually part of the held trigger, is released. Releasing an
// unrelated modifier (e.g. Shift while holding a bare "a") must NOT reset.
Iif (!pressedRef.current) {
return;
}
const released = event.key.toLowerCase();
const modifierFlag = MODIFIER_KEY_TO_FLAG[event.key];
const isTriggerModifierRelease =
modifierFlag !== undefined &&
triggerModifiersRef.current?.[modifierFlag] === true;
if (released === triggerKeyRef.current || isTriggerModifierRelease) {
triggerKeyRef.current = null;
triggerModifiersRef.current = null;
setPressedState(false);
config.onRelease?.(event);
}
},
[setPressedState]
);
// Focus left the window while a key was held: keyup will never arrive, so
// reset. Fire onRelease with a synthetic keyup so onPress/onRelease stay
// balanced instead of leaking a dangling press. Registered directly on the
// blur event, so it must NOT be `resetPressed` (which would receive the raw
// blur Event and mistake it for a KeyboardEvent).
const handleBlur = useCallback(() => {
if (!pressedRef.current) {
return;
}
const synthetic =
typeof KeyboardEvent !== "undefined"
? new KeyboardEvent("keyup")
: undefined;
resetPressed(synthetic);
}, [resetPressed]);
useEffect(() => {
if (!isKeyPressSupported() || !enabled) {
// Reset any lingering pressed state when disabled or unsupported.
resetPressed();
return;
}
const element = resolveTarget(eventTarget);
if (!element) {
return;
}
const listenDown = eventType === "both" || eventType === "keydown";
const listenUp = eventType === "both" || eventType === "keyup";
if (listenDown) {
element.addEventListener("keydown", handleKeyDown as EventListener);
}
if (listenUp) {
element.addEventListener("keyup", handleKeyUp as EventListener);
}
// Reset on blur so a key held while focus leaves the window/tab does not
// remain "pressed" forever (keyup is never delivered in that case).
const win = typeof window !== "undefined" ? window : null;
win?.addEventListener("blur", handleBlur);
return () => {
if (listenDown) {
element.removeEventListener("keydown", handleKeyDown as EventListener);
}
if (listenUp) {
element.removeEventListener("keyup", handleKeyUp as EventListener);
}
win?.removeEventListener("blur", handleBlur);
};
}, [
enabled,
eventTarget,
eventType,
handleKeyDown,
handleKeyUp,
handleBlur,
resetPressed,
]);
return pressed;
}
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