51 lines
1.7 KiB
TypeScript
51 lines
1.7 KiB
TypeScript
/*
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Copyright 2019 The Matrix.org Foundation C.I.C.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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import {useRef, useEffect} from "react";
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import type {EventEmitter} from "events";
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type Handler = (...args: any[]) => void;
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// Hook to wrap event emitter on and removeListener in hook lifecycle
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export const useEventEmitter = (emitter: EventEmitter, eventName: string | symbol, handler: Handler) => {
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// Create a ref that stores handler
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const savedHandler = useRef(handler);
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// Update ref.current value if handler changes.
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useEffect(() => {
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savedHandler.current = handler;
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}, [handler]);
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useEffect(
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() => {
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// allow disabling this hook by passing a falsy emitter
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if (!emitter) return;
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// Create event listener that calls handler function stored in ref
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const eventListener = (...args) => savedHandler.current(...args);
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// Add event listener
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emitter.on(eventName, eventListener);
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// Remove event listener on cleanup
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return () => {
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emitter.removeListener(eventName, eventListener);
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};
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},
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[eventName, emitter], // Re-run if eventName or emitter changes
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);
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};
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