Solid Principles: A Software Developer’s Framework to Robust, Maintainable Code(khalilstemmler.com)

    abstract class Employee {
    // This needs to be implemented
    abstract calculatePay (): number;
    // This needs to be implemented
    abstract reportHours (): number;
    // let's assume THIS is going to be the 
    // same algorithm for each employee- it can
    // be shared here.
    protected save (): Promise<any> {
        // common save algorithm
    }
    }

    class HR extends Employee {
    calculatePay (): number {
        // implement own algorithm
    }
    reportHours (): number {
        // implement own algorithm
    }
    }

    class Accounting extends Employee {
    calculatePay (): number {
        // implement own algorithm
    }
    reportHours (): number {
        // implement own algorithm
    }

    }

    class IT extends Employee {
    ...
    }

    class HR {
    calculatePay (Employee e): number {
        // implement own algorithm
    }
    reportHours (Employee e): number {
        // implement own algorithm
    }
    }

   bool is_prime(int n)