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These are examples from the book JavaScript: The Definitive Guide, 6th Edition.

See the "O'Reilly Policy on Re-Use of Code Examples from Books"

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documentation of your program, with a comment like the following:

// This code is from the book JavaScript: The Definitive Guide, 6th Edition,

// (ISBN #978-0596805524). Copyright 2011 by David Flanagan.

Please note that the examples are not production code and have not been

carefully testing. They are provided "as-is" and come with no warranty

of any kind.

## Example files for the title:  

# JavaScript: The Definitive Guide 6th Edition, by David Flanagan

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<!DOCTYPE html>   

<html>

<head>

<title>JavaScript Loan Calculator</title>

<style> /* This is a CSS style sheet: it adds style to the program output */

.output { font-weight: bold; }           /* Calculated values in bold */

#payment { text-decoration: underline; } /* For element with id="payment" */

#graph { border: solid black 1px; }      /* Chart has a simple border */

th, td { vertical-align: top; }          /* Don't center table cells */

</style>

</head>

<body>

<!--

  This is an HTML table with <input> elements that allow the user to enter data

  and <span> elements in which the program can display its results.

  These elements have ids like "interest" and "years". These ids are used

  in the JavaScript code that follows the table. Note that some of the input

  elements define "onchange" or "onclick" event handlers. These specify strings

  of JavaScript code to be executed when the user enters data or clicks.

-->

<table>

  <tr><th>Enter Loan Data:</th>

      <td></td>

      <th>Loan Balance, Cumulative Equity, and Interest Payments</th></tr>

  <tr><td>Amount of the loan ($):</td>

      <td><input id="amount" onchange="calculate();"></td>

      <td rowspan=8>

         <canvas id="graph" width="400" height="250"></canvas></td></tr>

  <tr><td>Annual interest (%):</td>

      <td><input id="apr" onchange="calculate();"></td></tr>

  <tr><td>Repayment period (years):</td>

      <td><input id="years" onchange="calculate();"></td>

  <tr><td>Zipcode (to find lenders):</td>

      <td><input id="zipcode" onchange="calculate();"></td>

  <tr><th>Approximate Payments:</th>

      <td><button onclick="calculate();">Calculate</button></td></tr>

  <tr><td>Monthly payment:</td>

      <td>$<span class="output" id="payment"></span></td></tr>

  <tr><td>Total payment:</td>

      <td>$<span class="output" id="total"></span></td></tr>

  <tr><td>Total interest:</td>

      <td>$<span class="output" id="totalinterest"></span></td></tr>

  <tr><th>Sponsors:</th><td  colspan=2>

    Apply for your loan with one of these fine lenders:

    <div id="lenders"></div></td></tr>

</table>

<!-- The rest of this example is JavaScript code in the <script> tag below -->

<!-- Normally, this script would go in the document <head> above but it -->

<!-- is easier to understand here, after you've seen its HTML context. -->

<script>

"use strict"; // Use ECMAScript 5 strict mode in browsers that support it

/*

 * This script defines the calculate() function called by the event handlers

 * in HTML above. The function reads values from <input> elements, calculates

 * loan payment information, displays the results in <span> elements. It also

 * saves the user's data, displays links to lenders, and draws a chart.

 */

function calculate() {

    // Look up the input and output elements in the document

    var amount = document.getElementById("amount");

    var apr = document.getElementById("apr");

    var years = document.getElementById("years");

    var zipcode = document.getElementById("zipcode");

    var payment = document.getElementById("payment");

    var total = document.getElementById("total");

    var totalinterest = document.getElementById("totalinterest");

    // Get the user's input from the input elements. Assume it is all valid.

    // Convert interest from a percentage to a decimal, and convert from

    // an annual rate to a monthly rate. Convert payment period in years

    // to the number of monthly payments.

    var principal = parseFloat(amount.value);

    var interest = parseFloat(apr.value) / 100 / 12;

    var payments = parseFloat(years.value) * 12;

    // Now compute the monthly payment figure.

    var x = Math.pow(1 + interest, payments);   // Math.pow() computes powers

    var monthly = (principal*x*interest)/(x-1);

    // If the result is a finite number, the user's input was good and

    // we have meaningful results to display

    if (isFinite(monthly)) {

        // Fill in the output fields, rounding to 2 decimal places

        payment.innerHTML = monthly.toFixed(2);

        total.innerHTML = (monthly * payments).toFixed(2);

        totalinterest.innerHTML = ((monthly*payments)-principal).toFixed(2);

        // Save the user's input so we can restore it the next time they visit

        save(amount.value, apr.value, years.value, zipcode.value);

        // Advertise: find and display local lenders, but ignore network errors

        try {      // Catch any errors that occur within these curly braces

            getLenders(amount.value, apr.value, years.value, zipcode.value);

        }

        catch(e) { /* And ignore those errors */ }

        // Finally, chart loan balance, and interest and equity payments

        chart(principal, interest, monthly, payments);

    }

    else {  

        // Result was Not-a-Number or infinite, which means the input was

        // incomplete or invalid. Clear any previously displayed output.

        payment.innerHTML = "";        // Erase the content of these elements

        total.innerHTML = ""

        totalinterest.innerHTML = "";

        chart();                       // With no arguments, clears the chart

    }

}

// Save the user's input as properties of the localStorage object. Those

// properties will still be there when the user visits in the future

// This storage feature will not work in some browsers (Firefox, e.g.) if you 

// run the example from a local file:// URL.  It does work over HTTP, however.

function save(amount, apr, years, zipcode) {

    if (window.localStorage) {  // Only do this if the browser supports it

        localStorage.loan_amount = amount;

        localStorage.loan_apr = apr;

        localStorage.loan_years = years;

        localStorage.loan_zipcode = zipcode;

    }

}

// Automatically attempt to restore input fields when the document first loads.

window.onload = function() {

    // If the browser supports localStorage and we have some stored data

    if (window.localStorage && localStorage.loan_amount) {  

        document.getElementById("amount").value = localStorage.loan_amount;

        document.getElementById("apr").value = localStorage.loan_apr;

        document.getElementById("years").value = localStorage.loan_years;

        document.getElementById("zipcode").value = localStorage.loan_zipcode;

    }

};

// Pass the user's input to a server-side script which can (in theory) return

// a list of links to local lenders interested in making loans.  This example

// does not actually include a working implementation of such a lender-finding

// service. But if the service existed, this function would work with it.

function getLenders(amount, apr, years, zipcode) {

    // If the browser does not support the XMLHttpRequest object, do nothing

    if (!window.XMLHttpRequest) return;

    // Find the element to display the list of lenders in

    var ad = document.getElementById("lenders");

    if (!ad) return;                            // Quit if no spot for output 

    // Encode the user's input as query parameters in a URL

    var url = "getLenders.php" +                // Service url plus

        "?amt=" + encodeURIComponent(amount) +  // user data in query string

        "&apr=" + encodeURIComponent(apr) +

        "&yrs=" + encodeURIComponent(years) +

        "&zip=" + encodeURIComponent(zipcode);

    // Fetch the contents of that URL using the XMLHttpRequest object

    var req = new XMLHttpRequest();        // Begin a new request

    req.open("GET", url);                  // An HTTP GET request for the url

    req.send(null);                        // Send the request with no body

    // Before returning, register an event handler function that will be called

    // at some later time when the HTTP server's response arrives. This kind of 

    // asynchronous programming is very common in client-side JavaScript.

    req.onreadystatechange = function() {

        if (req.readyState == 4 && req.status == 200) {

            // If we get here, we got a complete valid HTTP response

            var response = req.responseText;     // HTTP response as a string

            var lenders = JSON.parse(response);  // Parse it to a JS array

            // Convert the array of lender objects to a string of HTML

            var list = "";

            for(var i = 0; i < lenders.length; i++) {

                list += "<li><a href='" + lenders[i].url + "'>" +

                    lenders[i].name + "</a>";

            }

            // Display the HTML in the element from above.

            ad.innerHTML = "<ul>" + list + "</ul>"; 

        }

    }

}

// Chart monthly loan balance, interest and equity in an HTML <canvas> element.

// If called with no arguments then just erase any previously drawn chart.

function chart(principal, interest, monthly, payments) {

    var graph = document.getElementById("graph"); // Get the <canvas> tag

    graph.width = graph.width;  // Magic to clear and reset the canvas element

    // If we're called with no arguments, or if this browser does not support

    // graphics in a <canvas> element, then just return now.

    if (arguments.length == 0 || !graph.getContext) return;

    // Get the "context" object for the <canvas> that defines the drawing API

    var g = graph.getContext("2d"); // All drawing is done with this object

    var width = graph.width, height = graph.height; // Get canvas size

    // These functions convert payment numbers and dollar amounts to pixels

    function paymentToX(n) { return n * width/payments; }

    function amountToY(a) { return height-(a * height/(monthly*payments*1.05));}

    // Payments are a straight line from (0,0) to (payments, monthly*payments)

    g.moveTo(paymentToX(0), amountToY(0));         // Start at lower left

    g.lineTo(paymentToX(payments),                 // Draw to upper right

             amountToY(monthly*payments));

    g.lineTo(paymentToX(payments), amountToY(0));  // Down to lower right

    g.closePath();                                 // And back to start

    g.fillStyle = "#f88";                          // Light red

    g.fill();                                      // Fill the triangle

    g.font = "bold 12px sans-serif";               // Define a font

    g.fillText("Total Interest Payments", 20,20);  // Draw text in legend

    // Cumulative equity is non-linear and trickier to chart

    var equity = 0;

    g.beginPath();                                 // Begin a new shape

    g.moveTo(paymentToX(0), amountToY(0));         // starting at lower-left

    for(var p = 1; p <= payments; p++) {

        // For each payment, figure out how much is interest

        var thisMonthsInterest = (principal-equity)*interest;

        equity += (monthly - thisMonthsInterest);  // The rest goes to equity

        g.lineTo(paymentToX(p),amountToY(equity)); // Line to this point

    }

    g.lineTo(paymentToX(payments), amountToY(0));  // Line back to X axis

    g.closePath();                                 // And back to start point

    g.fillStyle = "green";                         // Now use green paint

    g.fill();                                      // And fill area under curve

    g.fillText("Total Equity", 20,35);             // Label it in green

    // Loop again, as above, but chart loan balance as a thick black line

    var bal = principal;

    g.beginPath();

    g.moveTo(paymentToX(0),amountToY(bal));

    for(var p = 1; p <= payments; p++) {

        var thisMonthsInterest = bal*interest;

        bal -= (monthly - thisMonthsInterest);     // The rest goes to equity

        g.lineTo(paymentToX(p),amountToY(bal));    // Draw line to this point

    }

    g.lineWidth = 3;                               // Use a thick line

    g.stroke();                                    // Draw the balance curve

    g.fillStyle = "black";                         // Switch to black text

    g.fillText("Loan Balance", 20,50);             // Legend entry

    // Now make yearly tick marks and year numbers on X axis

    g.textAlign="center";                          // Center text over ticks

    var y = amountToY(0);                          // Y coordinate of X axis

    for(var year=1; year*12 <= payments; year++) { // For each year

        var x = paymentToX(year*12);               // Compute tick position

        g.fillRect(x-0.5,y-3,1,3);                 // Draw the tick

        if (year == 1) g.fillText("Year", x, y-5); // Label the axis

        if (year % 5 == 0 && year*12 !== payments) // Number every 5 years

            g.fillText(String(year), x, y-5);

    }

    // Mark payment amounts along the right edge

    g.textAlign = "right";                         // Right-justify text

    g.textBaseline = "middle";                     // Center it vertically

    var ticks = [monthly*payments, principal];     // The two points we'll mark

    var rightEdge = paymentToX(payments);          // X coordinate of Y axis

    for(var i = 0; i < ticks.length; i++) {        // For each of the 2 points

        var y = amountToY(ticks[i]);               // Compute Y position of tick

        g.fillRect(rightEdge-3, y-0.5, 3,1);       // Draw the tick mark

        g.fillText(String(ticks[i].toFixed(0)),    // And label it.

                   rightEdge-5, y);

    }

}

</script>

</body>

</html>

// inherit() returns a newly created object that inherits properties from the

// prototype object p.  It uses the ECMAScript 5 function Object.create() if

// it is defined, and otherwise falls back to an older technique.

function inherit(p) {

    if (p == null) throw TypeError(); // p must be a non-null object

    if (Object.create)                // If Object.create() is defined...

        return Object.create(p);      //    then just use it.

    var t = typeof p;                 // Otherwise do some more type checking

    if (t !== "object" && t !== "function") throw TypeError();

    function f() {};                  // Define a dummy constructor function.

    f.prototype = p;                  // Set its prototype property to p.

    return new f();                   // Use f() to create an "heir" of p.

}