export type EventListener = () => void;
export type EventTargetLike = {
addEventListener(
type: string,
listener: EventListener,
options?: boolean | { signal?: AbortSignal | null },
): void;
removeEventListener(type: string, listener: EventListener): void;
dispatchEvent(event: { type: string }): void;
};
class SimpleEventTarget implements EventTargetLike {
private listeners = new Map<string, Set<EventListener>>();
addEventListener(
type: string,
listener: EventListener,
options?: boolean | { signal?: AbortSignal | null },
) {
let bucket = this.listeners.get(type);
if (!bucket) {
bucket = new Set();
this.listeners.set(type, bucket);
}
bucket.add(listener);
if (options && typeof options === "object" && options.signal) {
const signal = options.signal;
if (signal.aborted) {
bucket.delete(listener);
return;
}
const onAbort = () => {
bucket?.delete(listener);
signal.removeEventListener?.("abort", onAbort);
};
signal.addEventListener?.("abort", onAbort, { once: true });
}
}
removeEventListener(type: string, listener: EventListener) {
this.listeners.get(type)?.delete(listener);
}
dispatchEvent(event: { type: string }) {
const bucket = this.listeners.get(event.type);
if (!bucket) return;
for (const listener of bucket) {
listener();
}
}
}
export function createEventTarget(): EventTargetLike {
return new SimpleEventTarget();
}
