Typescript error on callback function: Type 'Function' provides no match for the signature

Question

I'm an error that Type 'Function' provides no match for the signature for the filter below. Which is true because filter expects a specific type. How would define my callback to match what filter expects?

private _getItemFilteredBy(itemName: string, Fn: Function): Observable<any[]> {
    return this.getItemByName(itemName)
        .map((items: any[]) => {
            return items.filter( Fn );
        });
}

Answer 1

Filter needs a predicate. Change the type to (x:any) => boolean

private _getItemFilteredBy(itemName: string, Fn: (x:any) => boolean): Observable<any[]> {
    return this.getItemByName(itemName)
        .map((items: any[]) => {
            return items.filter( Fn );
        });
}

If you have more specific type information than 'any', I'd recommend updating that too but what I've posted above should work.