EventEmitter.ts

type BaseEventsMap = {
    [key: string]: any[]; // ключ - название события, значение - возможные аргументы
};

type Callback<P extends any[]> = (...payload: P) => void;

class EventEmitter<EventsMap extends BaseEventsMap> {
    events: Map<keyof EventsMap, Set<Callback<EventsMap[keyof EventsMap]>>> = new Map();

    on<E extends keyof EventsMap>(event: E, callback: Callback<EventsMap[E]>): Function {
        if (!this.events.has(event)) {
            this.events.set(event, new Set());
        }

        const subscribers = this.events.get(event);

        subscribers.add(callback);

        return () => subscribers.delete(callback);
    }

    off<E extends keyof EventsMap>(event: E, callback: Callback<EventsMap[E]>) {
        if (!this.events.has(event)) {
            return;
        }

        this.events.get(event).delete(callback);
    }

    emit<E extends keyof EventsMap>(event: E, ...payload: EventsMap[E]) {
        if (!this.events.has(event)) {
            return;
        }

        this.events.get(event).forEach((callback) => {
            callback(...payload);
        });
    }
}

type MyEventsMap = {
    foo: [];
    bar: [number];
};

const emitter = new EventEmitter<MyEventsMap>();

emitter.on('foo', () => {

});

emitter.on('bar', (a) => {

});

emitter.on('baz', (a) => {

});

emitter.emit('foo', '');

emitter.emit('bar', 1);

export { EventEmitter };

type BaseEventsMap = {
    [key: string]: (...args: any[]) => void; // ключ - название события, значение - возможные аргументы
};

type Callback<P extends any[]> = (...payload: P) => void;

class EventEmitter<EventsMap extends BaseEventsMap> {
    events: Map<keyof EventsMap, Set<Callback<Parameters<EventsMap[keyof EventsMap]>>>> = new Map();

    on<E extends keyof EventsMap>(event: E, callback: Callback<Parameters<EventsMap[E]>>): Function {
        if (!this.events.has(event)) {
            this.events.set(event, new Set());
        }

        const subscribers = this.events.get(event);

        subscribers.add(callback);

        return () => subscribers.delete(callback);
    }

    off<E extends keyof EventsMap>(event: E, callback: Callback<Parameters<EventsMap[E]>>) {
        if (!this.events.has(event)) {
            return;
        }

        this.events.get(event).delete(callback);
    }

    emit<E extends keyof EventsMap>(event: E, ...payload: Parameters<EventsMap[E]>) {
        if (!this.events.has(event)) {
            return;
        }

        this.events.get(event).forEach((callback) => {
            callback(...payload);
        });
    }
}

type MyEventsMap = {
    foo: () => void;
    bar: (a: number, b: string) => void;
};

const emitter = new EventEmitter<MyEventsMap>();

const handler: MyEventsMap['bar'] = (a, b) => {
    console.log(a)
}

emitter.on('foo', () => {

});

emitter.on('bar', handler);

emitter.on('baz', (a) => {

});

emitter.emit('foo', '');

emitter.emit('bar', 1);

export { EventEmitter };