tax-calculator-breakdowns-brackets

tax-calculator-breakdowns-brackets.js

'use strict';

const personalAllowance = 25000;

const calculateTaxes = (taxBrackets, taxableAllowance) => {
	const taxInfo = taxBrackets.reduce(
		(accumulator, taxBracket) => {
			if (accumulator.remainingAmountToBeTaxed <= 0) {
				return accumulator;
			}

			const amtToTax =
				taxBracket.amount && accumulator.remainingAmountToBeTaxed > taxBracket.amount
					? taxBracket.amount
					: accumulator.remainingAmountToBeTaxed;

			accumulator.taxAccrued += amtToTax * (taxBracket.percent / 100);
			accumulator.remainingAmountToBeTaxed -= amtToTax;

			accumulator.breakdowns.push({
				taxBracket,
				amountTaxed: amtToTax,
				taxAccrued: accumulator.taxAccrued,
				remainingAmountToBeTaxed: accumulator.remainingAmountToBeTaxed
			});

			return accumulator;
		},
		{
			taxAccrued: 0,
			remainingAmountToBeTaxed: taxableAllowance,
			breakdowns: []
		}
	);

	return taxInfo;
};

const calcTaxesPreJuly2019 = annualPay => {
	const taxableAllowance = annualPay - personalAllowance;

	const taxBrackets = [{ amount: 35000, percent: 16 }, { amount: 15000, percent: 33.5 }, { percent: 40 }];

	const taxInfo = calculateTaxes(taxBrackets, taxableAllowance);

	return taxInfo;
};

const calcTaxesPostJuly2019 = annualPay => {
	const taxableAllowance = annualPay - personalAllowance;

	const taxBrackets = [{ amount: 50000, percent: 12.5 }, { percent: 33.5 }];

	const taxInfo = calculateTaxes(taxBrackets, taxableAllowance);

	return taxInfo;
};

const calcTaxesJan2020 = annualPay => {
	const taxableAllowance = annualPay - personalAllowance;

	const taxBrackets = [{ amount: 50000, percent: 12.5 }, { percent: 28.5 }];

	const taxInfo = calculateTaxes(taxBrackets, taxableAllowance);

	return taxInfo;
};

console.log(JSON.stringify(calcTaxesPreJuly2019(25001 - 2)));
console.log(JSON.stringify(calcTaxesPreJuly2019(25001)));
console.log(JSON.stringify(calcTaxesPreJuly2019(150001)));
console.log(JSON.stringify(calcTaxesPostJuly2019(150001)));
console.log(JSON.stringify(calcTaxesJan2020(150001)));