expo-key-event/src/hooks/useKeyEventListener.web.ts

Provides an interface for reading key events such as from external bluetooth keyboards on Android, iOS and Web.

import { useCallback, useEffect } from "react";

import { KeyPressEvent, KeyReleaseEvent } from "../ExpoKeyEvent.types";

export interface UseKeyEventListenerOptions {
  /**
   * Pass 'false' to prevent automatic key event listening
   * - Use startListening/stopListening to control the listener manually
   * @default true
   */
  listenOnMount?: boolean;
  /**
   * Prevent reloading the app when pressing 'r' (not applicable on web)
   * @default false
   */
  preventReload?: boolean;
  /**
   * Pass 'true' to enable onKeyRelease events (defaults to false for backward compatibility)
   * @default false
   */
  listenToRelease?: boolean;
}

// New API - listener + options object
export function useKeyEventListener(
  listener: (event: KeyPressEvent | KeyReleaseEvent) => void,
  options?: UseKeyEventListenerOptions,
): ReturnType<typeof useKeyEventListenerImpl>;
/**
 * Legacy API - listener + positional parameters (for backwards compatibility)
 * @deprecated Use `useKeyEvent(
  options?: UseKeyEventOptions
)` instead
 */
export function useKeyEventListener(
  listener: (event: KeyPressEvent | KeyReleaseEvent) => void,
  listenOnMount?: boolean,
  preventReload?: boolean,
  listenToRelease?: boolean,
): ReturnType<typeof useKeyEventListenerImpl>;

export function useKeyEventListener(
  listener: (event: KeyPressEvent | KeyReleaseEvent) => void,
  optionsOrListenOnMount?: UseKeyEventListenerOptions | boolean,
  preventReload?: boolean,
  listenToRelease?: boolean,
) {
  // Backwards compatibility: detect if using old API (boolean) or new API (object/undefined)
  let options: UseKeyEventListenerOptions;

  if (typeof optionsOrListenOnMount === "boolean") {
    // Legacy API: positional parameters (boolean explicitly passed)
    options = {
      listenOnMount: optionsOrListenOnMount,
      preventReload: preventReload ?? false,
      listenToRelease: listenToRelease ?? false,
    };
  } else {
    // New API: options object or undefined (defaults to {})
    options = optionsOrListenOnMount ?? {};
  }

  return useKeyEventListenerImpl(listener, options);
}

function useKeyEventListenerImpl(
  listener: (event: KeyPressEvent | KeyReleaseEvent) => void,
  {
    listenOnMount = true,
    preventReload = false,
    listenToRelease = false,
  }: UseKeyEventListenerOptions,
) {
  const onKeyDown = useCallback(
    (event: KeyboardEvent) => listener({ key: event.code, eventType: "press" }),
    [listener],
  );

  const onKeyUp = useCallback(
    (event: KeyboardEvent) =>
      listener({ key: event.code, eventType: "release" }),
    [listener],
  );

  const startListening = useCallback(() => {
    addEventListener("keydown", onKeyDown);
    if (listenToRelease) {
      addEventListener("keyup", onKeyUp);
    }
  }, [onKeyDown, onKeyUp, listenToRelease]);

  const stopListening = useCallback(() => {
    removeEventListener("keydown", onKeyDown);
    if (listenToRelease) {
      removeEventListener("keyup", onKeyUp);
    }
  }, [onKeyDown, onKeyUp, listenToRelease]);

  useEffect(() => {
    if (listenOnMount) startListening();

    return () => {
      stopListening();
    };
  }, [listenOnMount, startListening, stopListening]);

  return {
    /**
     * Start listening for key events
     */
    startListening,
    /**
     * Stop listening for key events
     */
    stopListening,
  };
}