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Tonymif

•Created by Tonymif on 3/29/2024 in #questions

Generic EventEmitter Class

I am trying to make the eventEmitter class generic, however many type errors occur such as:

Property 'emit' in type 'TypedEventEmitter<T>' is not assignable to the same property in base type 'EventEmitter<string | symbol, any>'.

type EventEmitterTypes<T> = {
    [K in keyof T]: (payload: any) => void;
};


class TypedEventEmitter<T> extends EventEmitter {
    emit<K extends keyof EventEmitterTypes<T>>(event: K, payload: any): boolean {
        return super.emit(event as string, payload);
    }

    on<K extends keyof EventEmitterTypes<T>>(event: K, listener: EventEmitterTypes<T>[K]): this {
        return super.on(event as string, listener);
    }

    off<K extends keyof EventEmitterTypes<T>>(event: K, listener: EventEmitterTypes<T>[K]): this {
        return super.off(event as string, listener);
    }

    once<K extends keyof EventEmitterTypes<T>>(event: K, listener: EventEmitterTypes<T>[K]): this {
        return super.once(event as string, listener);
    }
}

type EventEmitterTypes<T> = {
    [K in keyof T]: (payload: any) => void;
};


class TypedEventEmitter<T> extends EventEmitter {
    emit<K extends keyof EventEmitterTypes<T>>(event: K, payload: any): boolean {
        return super.emit(event as string, payload);
    }

    on<K extends keyof EventEmitterTypes<T>>(event: K, listener: EventEmitterTypes<T>[K]): this {
        return super.on(event as string, listener);
    }

    off<K extends keyof EventEmitterTypes<T>>(event: K, listener: EventEmitterTypes<T>[K]): this {
        return super.off(event as string, listener);
    }

    once<K extends keyof EventEmitterTypes<T>>(event: K, listener: EventEmitterTypes<T>[K]): this {
        return super.once(event as string, listener);
    }
}

Does anyone know how to fix this? TIA

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