Using classes in ES6

js/mortgage.js

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+export let calculateMonthlyPayment = (principal, years, rate) => {
+    let monthlyRate = 0;
+    if (rate) {
+        monthlyRate = rate / 100 / 12;
+    }
+    let monthlyPayment = principal * monthlyRate / (1 - (Math.pow(1 / (1 + monthlyRate), years * 12)));
+    return {principal, years, rate, monthlyPayment, monthlyRate};
+    // Creating Objects from Variables ## ES6
+    // shorted for the following ES5 syntax
+    // return { principal: principal,
+    //      years: years,
+    //      rate: rate,
+    //      monthlyPayment: monthlyPayment,
+    //      monthlyRate: monthlyRate };
+};
+export let calculateAmortization = (principal, years, rate) => {
+    let {monthlyRate, monthlyPayment} = calculateMonthlyPayment(principal, years, rate);
+    let balance = principal;
+    let amortization = [];
+    for (let y=0; y<years; y++) {
+        let interestY = 0; // Interest payment for year y
+        let principalY = 0; // principal payment for year y
+        for (let m=0; m<12; m++) {
+            let interestM = balance * monthlyRate; // Interest payment for month m
+            let principalM = monthlyPayment - interestM; //principal payment for month m
+            interestY = interestY + interestM;
+            principalY = principalY + principalM;
+            balance = balance - principalM;
+        }
+        amortization.push({principalY, interestY, balance})
+    }
+    return {monthlyPayment, monthlyRate, amortization};
+};