/**
 * Filters an object type to include only properties whose values
 * are assignable to a specified `ValueType`.
 */
type FilterPropertiesByValueType<T, ValueType> = {
    [P in keyof T as T[P] extends ValueType ? P : never]: T[P];
};

interface Employee {
    id: string;
    name: string;
    age: number;
    email: string;
    isActive: boolean;
    hiredDate: Date;
    departmentId: number | null;
}

// Get properties that are strings
type StringProperties = FilterPropertiesByValueType<Employee, string>;
/*
type StringProperties = {
    id: string;
    name: string;
    email: string;
}
*/

// Get properties that are numbers
type NumberProperties = FilterPropertiesByValueType<Employee, number>;
/*
type NumberProperties = {
    age: number;
}
*/

// Get properties that are boolean
type BooleanProperties = FilterPropertiesByValueType<Employee, boolean>;
/*
type BooleanProperties = {
    isActive: boolean;
}
*/

// Get properties that are nullable numbers (number | null)
type NullableNumberProperties = FilterPropertiesByValueType<Employee, number | null>;
/*
type NullableNumberProperties = {
    age: number;
    departmentId: number | null;
}
*/

// Get properties that are objects (excluding null)
type ObjectProperties = FilterPropertiesByValueType<Employee, object>;
/*
type ObjectProperties = {
    hiredDate: Date; // Date is an object
}
*/