A contrived declarative approach of declarative programming

credit-card-processing-declarative.ts

interface PaymentMethod {
    process(amount: number): void;
}

const paymentMethods: Record<string, PaymentMethod> = {
    credit: {
        process(amount: number) {
            console.log(`Processing $${amount} via Credit Card`);
            // Credit card processing logic...
        }
    },
    paypal: {
        process(amount: number) {
            console.log(`Processing $${amount} via PayPal`);
            // PayPal processing logic...
        }
    },
    bank_transfer: {
        process(amount: number) {
            console.log(`Processing $${amount} via Bank Transfer`);
            // Bank transfer processing logic...
        }
    }
    // Add more methods as needed...
};

function processPayment(amount: number, method: string) {
    const processor = paymentMethods[method];
    if (!processor) {
        throw new Error('Unsupported payment method');
    }
    processor.process(amount);
}