Tom Boullay
62 lines
1.3 KiB
TypeScript
62 lines
1.3 KiB
TypeScript
type Listener<TPayload> = (payload: TPayload) => void;
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type ListenerMap<TEvents extends object> = {
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[TKey in keyof TEvents]?: Set<Listener<TEvents[TKey]>>;
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};
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export class EventEmitter<TEvents extends object> {
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private readonly listeners: ListenerMap<TEvents> = {};
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on<TKey extends keyof TEvents>(
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event: TKey,
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listener: Listener<TEvents[TKey]>,
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): () => void {
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const existing = this.listeners[event];
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if (existing) {
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existing.add(listener);
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} else {
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this.listeners[event] = new Set([listener]);
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}
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return () => {
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this.off(event, listener);
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};
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}
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off<TKey extends keyof TEvents>(
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event: TKey,
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listener: Listener<TEvents[TKey]>,
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): void {
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const currentListeners = this.listeners[event];
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if (!currentListeners) {
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return;
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}
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currentListeners.delete(listener);
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if (currentListeners.size === 0) {
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delete this.listeners[event];
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}
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}
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emit<TKey extends keyof TEvents>(event: TKey, payload: TEvents[TKey]): void {
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const currentListeners = this.listeners[event];
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if (!currentListeners) {
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return;
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}
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currentListeners.forEach((listener) => {
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listener(payload);
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});
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}
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clear(): void {
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for (const key of Object.keys(this.listeners) as (keyof TEvents)[]) {
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delete this.listeners[key];
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}
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}
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}
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