Subscription Period Calculator

A simple and efficient TypeScript function to calculate subscription periods for monthly and yearly subscriptions.

Installation

You can install this package using npm:

npm install subscription-period-calculator

Usage

Here's how you can use the calculateSubscriptionPeriod function:

import { calculateSubscriptionPeriod } from 'subscription-period-calculator';

// Calculate yearly subscription period
const yearlyStart = new Date('2023-07-31T01:08:34.000Z');
const yearlyResult = calculateSubscriptionPeriod('yearly', 'start', yearlyStart);
console.log('Yearly subscription:');
console.log('Start:', yearlyResult.startDate);
console.log('End:', yearlyResult.endDate);

// Calculate monthly subscription period
const monthlyEnd = new Date('2023-07-31T01:08:34.000Z');
const monthlyResult = calculateSubscriptionPeriod('monthly', 'end', monthlyEnd);
console.log('Monthly subscription:');
console.log('Start:', monthlyResult.startDate);
console.log('End:', monthlyResult.endDate);

API

calculateSubscriptionPeriod(type, dateType, date) Calculates the start and end dates for a subscription period. Parameters:

• type (SubscriptionType): 'monthly' or 'yearly'
• dateType (DateInput): 'start' or 'end'
• date (Date): The known date (either start or end date of the subscription)

Returns: An object with startDate and endDate properties, both of type Date. Testing To run the tests locally:

1. Clone this repository
2. Install dependencies: npm install
3. Run the test script: npm test

The test script will run several test cases and output the results to the console.

Examples

Yearly Subscription

const yearlyStart = new Date('2023-07-31T01:08:34.000Z');
const result = calculateSubscriptionPeriod('yearly', 'start', yearlyStart);
// result.startDate: 2023-07-31T01:08:34.000Z
// result.endDate:   2024-07-31T01:08:34.000Z

Monthly Subscription

const monthlyEnd = new Date('2023-07-31T01:08:34.000Z');
const result = calculateSubscriptionPeriod('monthly', 'end', monthlyEnd);
// result.startDate: 2023-06-30T01:08:34.000Z
// result.endDate:   2023-07-31T01:08:34.000Z

Notes

• For monthly subscriptions, the function handles edge cases like months with different numbers of days.
• The function throws an error for invalid inputs (e.g., invalid date or subscription type).

License

This project is licensed under the MIT License.