lease-term-calculator

Calculate lease term duration in years and days.

Installation

npm install lease-term-calculator

Usage

import calculator from 'lease-term-calculator';
// or
import { DateCalculator } from 'lease-term-calculator';

const calc = new DateCalculator();

parseUIDate

Parses and validates date components.

const date = calculator.parseUIDate(2024, 6, 15);
// Returns: Date object, '' (empty input), or 'bad date'

calculateTermOfLease

Calculates the lease term between dates.

const effective = new Date(2024, 0, 1);
const start = new Date(2024, 0, 1);
const end = new Date(2026, 5, 30);

const result = calculator.calculateTermOfLease(effective, start, end);
// Returns: { years: 2, days: 181, daysInPartialYear: 365 }

Parameters:

• effectiveDate - The effective date (lease won't start before this)
• startDate - The lease start date
• endDate - The lease end date

Returns:

• years - Number of complete years
• days - Number of additional days beyond complete years
• daysInPartialYear - Total days in the partial year (for calculating fractions)

Validations:

The calculator performs comprehensive validation and throws errors for:

• Invalid date objects: All parameters must be valid Date objects
• Invalid dates: NaN dates or dates with invalid components
• Start after end: Start date cannot be after end date
• Same start and end: Start and end dates cannot be the same
• Year range: Years must be between 1900 and 2200

Error handling:

try {
  const result = calculator.calculateTermOfLease(
    new Date(2024, 0, 1),
    new Date(2026, 5, 30),  // Start after end
    new Date(2024, 0, 1)
  );
} catch (error) {
  console.error(error.message);
  // Output: "Start date cannot be after end date"
}

CommonJS Usage

The package supports both ES6 imports and CommonJS require:

// ES6
import { calculateTermOfLease } from 'lease-term-calculator';

// CommonJS
const { calculateTermOfLease } = require('lease-term-calculator');
// or
const calculator = require('lease-term-calculator');
calculator.calculateTermOfLease(effective, start, end);

License

MIT