'use strict';

var calculateMonthlyPayment = function calculateMonthlyPayment(principal, years, rate) {
    var monthlyRate = 0;
    if (rate) {
        monthlyRate = rate / 100 / 12;
    }
    var monthlyPayment = principal * monthlyRate / (1 - Math.pow(1 / (1 + monthlyRate), years * 12));
    return { principal: principal, years: years, rate: rate, monthlyPayment: monthlyPayment, monthlyRate: monthlyRate };
    // Creating Objects from Variables ## ES6
    // shorted for the following ES5 syntax
    // return { principal: principal,
    //      years: years,
    //      rate: rate,
    //      monthlyPayment: monthlyPayment,
    //      monthlyRate: monthlyRate };
};

document.getElementById('calcBtn').addEventListener('click', function () {
    var principal = document.getElementById("principal").value;
    var years = document.getElementById("years").value;
    var rate = document.getElementById("rate").value;

    var _calculateMonthlyPaym = calculateMonthlyPayment(principal, years, rate),
        monthlyPayment = _calculateMonthlyPaym.monthlyPayment,
        monthlyRate = _calculateMonthlyPaym.monthlyRate;

    document.getElementById("monthlyPayment").innerHTML = monthlyPayment.toFixed(2);
    document.getElementById("monthlyRate").innerHTML = (monthlyRate * 100).toFixed(2);
});