Details Example

MonthlyPayment Example -- Source Code

HTML Page -- index.htm

<!DOCTYPE html>

<!-- MonthlyPayment Example 
Source code file: index.htm
Compute monthly payment for a loan, using
principal, interest rate, and term of loan
in years.                              -->

<html lang="em">
    <head>
        <title>MonthlyPayment Example</title>
        <script src="mp2.js"></script>
    </head>
    <body>
        <h1>Monthly Payment Example</h1>
        <div id="ctrls">
            <input type="text" id="princ">&nbsp;
            <label for="princ">Principal</label><br><br>
            <input type="text" id="interest">&nbsp;
            <label for="interest">Interest</label><br><br>
            <input type="text" id="term">&nbsp;
            <label for="term">Term in Years</label><br><br>
            <hr><br>
            <button id="btn">
                Compute Monthly Payment
            </button><br><br>
            <input type="text" id="monthly">&nbsp;
            <label for="monthly">Monthly Payment</label>
        </div>
    </body>
</html>

Script Page -- mp2.js

 // Function to compute monthly payment,
// with inputs principal, interest rate,
// term of loan in years.
function computeMP(p, r, n) {
    var m = (p * r / 1200.0) /
        (1 - (1.0 + r / 1200.0) ** (-12.0 * n));
    return m;
}

// Click event handler for button
function onClickMethod( ) {
    var p = parseFloat(
        document.getElementById("princ").value);
    var r = parseFloat(
        document.getElementById("interest").value);
    var n = parseFloat(
        document.getElementById("term").value);
    var m = computeMP(p, r, n);
    var output = document.getElementById("monthly");

    // Round off m to two digits after the decimal point.
    var roundedM = Math.round(m * 100) / 100;

    // valueOf changes number to string.
    output.value = roundedM.valueOf( ); 

}

// Initialization function that adds click
// event handler to button
function init( ) {
    var button = document.getElementById("btn");
    button.addEventListener("click", onClickMethod);
}

// Execute init method when window loads.
window.addEventListener("load", init);