realestate-jp
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不動産関連のユーティリティ関数を提供するライブラリ
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JavaScript
;
Object.defineProperty(exports, "__esModule", { value: true });
exports.calcEqualPrincipal = calcEqualPrincipal;
const constants_js_1 = require("../constants.js");
const constants_js_2 = require("./constants.js");
const utils_js_1 = require("./utils.js");
/**
* 元金均等方式による住宅ローン返済を計算する（ボーナス加算対応）
*
* @param principal 借入金額（円）
* @param rate 年利（％、デフォルト: 1.5）
* @param years 返済年数（デフォルト: 35）
* @param downPayment 頭金（円、デフォルト: 0）
* @param annualBonus 年間ボーナス加算額（円、夏冬合計、デフォルト: 0）
* @returns ローン返済結果
*
* @example 使用例
* ```ts
* const result = calcEqualPrincipal(30000000, 1.5, 35, 5000000, 200000);
* console.log(result);
* ```
*/
function calcEqualPrincipal(principal, rate = constants_js_2.DEFAULT_LOAN_RATE, years = constants_js_2.DEFAULT_LOAN_YEARS, downPayment = 0, annualBonus = 0) {
const loanAmount = principal - downPayment;
const months = years * constants_js_1.MONTHS_PER_YEAR;
const monthlyPrincipal = loanAmount / months;
const bonusPerMonth = annualBonus / constants_js_2.BONUS_MONTHS.length;
let total = 0;
let normalSum = 0;
let bonusSum = 0;
let normalCount = 0;
let bonusCount = 0;
for (let i = 0; i < months; i++) {
const isBonus = (0, utils_js_1.isBonusMonth)(i);
const monthlyInterest = (0, utils_js_1.calculateMonthlyInterest)(loanAmount, monthlyPrincipal, i, rate);
const basePayment = monthlyPrincipal + monthlyInterest;
const payment = isBonus ? basePayment + bonusPerMonth : basePayment;
total += payment;
if (isBonus) {
bonusSum += payment;
bonusCount++;
}
else {
normalSum += payment;
normalCount++;
}
}
const avgMonthly = normalSum / normalCount;
const avgBonus = bonusSum / bonusCount;
const annual = (avgMonthly * normalCount + avgBonus * bonusCount) / years;
return {
monthly: Math.round(avgMonthly),
bonusMonth: Math.round(avgBonus),
annual: Math.round(annual),
total: Math.round(total),
};
}