BaseStore

code:base_store.ts

export type BaseStoreListenerInit<Event, Derived extends BaseStore<Event>> = {

store: Derived;

event: Event;

};

export type BaseStoreListener<Event, Derived extends BaseStore<Event>> = (

init: BaseStoreListenerInit<Event, Derived>,

) => void;

export class BaseStore<Event = string> {

constructor() {}

addChangeListener(listener: BaseStoreListener<Event, this>): void {

if (this._onChangeListeners.includes(listener)) {

throw new Error("already registerd");

}

this._onChangeListeners.push(listener);

}

removeChangeListener(listener: BaseStoreListener<Event, this>): void {

this._onChangeListeners = this._onChangeListeners.filter((l) => l !== listener);

}

emitChange(event: Event): void {

for (const listener of this._onChangeListeners) {

listener({ store: this, event });

}

}

get listenersCount(): number {

return this._onChangeListeners.length;

}

private _onChangeListeners: BaseStoreListener<Event, this>[] = [];

}