59 lines
1.3 KiB
JavaScript
59 lines
1.3 KiB
JavaScript
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//@ts-check
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/**
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* @template T
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* @typedef {(args:T) => void} Listener<T>
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*/
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/**
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* @typedef {{signal?: AbortSignal, once?: boolean}} ListenerOptions
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*/
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/**
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* Returns an event emitter for a specific signal
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* The initial passed value is optional, discarded, and only used to provide
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* automatic typing where applicable.
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* @template T
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* @param {T} [_initial]
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* @returns
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*/
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export const makeSignal = (_initial) => {
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/** @type {Set<Listener<T>>} */
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const listeners = new Set();
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let enabled = true
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/**
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*
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* @param {Listener<T>} fn
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* @param {ListenerOptions} [options]
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*/
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const connect = (fn, { once, signal } = {}) => {
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if (once) {
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const _bound = fn;
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fn = (args) => {
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listeners.delete(fn);
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_bound(args);
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};
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}
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listeners.add(fn);
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const _disconnect = () => disconnect(fn);
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signal && signal.addEventListener("abort", _disconnect);
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return _disconnect;
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};
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/**
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* @param {Listener<T>} fn
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* @returns
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*/
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const disconnect = (fn) => listeners.delete(fn);
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/**
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* @param {T} [args]
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* @returns
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*/
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// @ts-ignore
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const emit = (args) => enabled && listeners.forEach((fn) => fn(args));
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const disable = () => {enabled = false}
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return { connect, disconnect, emit, disable };
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};
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export default makeSignal
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