Universal Windows app samples

On GitHub Microsoft have published a lot of examples for Universal Apps: the link is https://github.com/Microsoft/Windows-universal-samples

This repo contains the samples that demonstrate the API usage patterns for the Universal Windows Platform (UWP) in the Windows Software Development Kit (SDK) for Windows 10. These code samples were created with the Universal Windows templates available in Visual Studio, and are designed to run on desktop, mobile, and future devices that support the Universal Windows Platform.

Universal Windows Platform development

These samples require Visual Studio 2015 and the Windows Software Development Kit (SDK) for Windows 10 to build, test, and deploy your Universal Windows apps.

Get a free copy of Visual Studio 2015 Community Edition with support for building Universal Windows apps

Additionally, to stay on top of the latest updates to Windows and the development tools, become a Windows Insider by joining the Windows Insider Program.

Become a Windows Insider

Using the samples

The easiest way to use these samples without using Git is to download the zip file containing the current version (using the link below or by clicking the "Download ZIP" button on the repo page). You can then unzip the samples and use them in Visual Studio 2015.

Download the samples ZIP

The samples use Linked files in Visual Studio to reduce duplication of common files, including sample template files and image assets. These common files are stored in the SharedContent folder at the root of the repository and referred to in the project files using links.

For more info about the programming models, platforms, languages, and APIs demonstrated in these samples, please refer to the guidance, tutorials, and reference topics provided in the Windows 10 documentation available in the Windows Developer Center. These samples are provided as-is in order to indicate or demonstrate the functionality of the programming models and feature APIs for Windows.

Classical Inheritance in JavaScript

JavaScript is a class-free, object-oriented language, and as such, it uses prototypal inheritance instead of classical inheritance. This can be puzzling to programmers trained in conventional object-oriented languages like C++ and Java. JavaScript's prototypal inheritance has more expressive power than classical inheritance, as we will see presently.

Java JavaScript
Strongly-typed Loosely-typed
Static Dynamic
Classical Prototypal
Classes Functions
Constructors Functions
Methods Functions

But first, why do we care about inheritance at all? There are primarily two reasons. The first is type convenience. We want the language system to automatically cast references of similar classes. Little type-safety is obtained from a type system which requires the routine explicit casting of object references. This is of critical importance in strongly-typed languages, but it is irrelevant in loosely-typed languages like JavaScript, where object references never need casting.

The second reason is code reuse. It is very common to have a quantity of objects all implementing exactly the same methods. Classes make it possible to create them all from a single set of definitions. It is also common to have objects that are similar to some other objects, but differing only in the addition or modification of a small number of methods. Classical inheritance is useful for this but prototypal inheritance is even more useful.

To demonstrate this, we will introduce a little sugar which will let us write in a style that resembles a conventional classical language. We will then show useful patterns which are not available in classical languages. Then finally, we will explain the sugar.

Classical Inheritance

First, we will make a Parenizor class that will have set and get methods for its value, and a toString method that will wrap the value in parens.

function Parenizor(value) {

Parenizor.method('setValue', function (value) {
    this.value = value;
    return this;

Parenizor.method('getValue', function () {
    return this.value;

Parenizor.method('toString', function () {
    return '(' + this.getValue() + ')';

The syntax is a little unusual, but it is easy to recognize the classical pattern in it. The method method takes a method name and a function, adding them to the class as a public method.

So now we can write

myParenizor = new Parenizor(0);
myString = myParenizor.toString();

As you would expect, myString is "(0)".

Now we will make another class which will inherit from Parenizor, which is the same except that its toString method will produce "-0-" if the value is zero or empty.

function ZParenizor(value) {


ZParenizor.method('toString', function () {
    if (this.getValue()) {
        return this.uber('toString');
    return "-0-";

The inherits method is similar to Java's extends. The uber method is similar to Java's super. It lets a method call a method of the parent class. (The names have been changed to avoid reserved word restrictions.)

So now we can write

myZParenizor = new ZParenizor(0);
myString = myZParenizor.toString();

This time, myString is "-0-".

JavaScript does not have classes, but we can program as though it does.

Multiple Inheritance

By manipulating a function's prototype object, we can implement multiple inheritance, allowing us to make a class built from the methods of multiple classes. Promiscuous multiple inheritance can be difficult to implement and can potentially suffer from method name collisions. We could implement promiscuous multiple inheritance in JavaScript, but for this example we will use a more disciplined form called Swiss Inheritance.

Suppose there is a NumberValue class that has a setValue method that checks that the value is a number in a certain range, throwing an exception if necessary. We only want its setValue and setRange methods for our ZParenizor. We certainly don't want its toString method. So, we write

ZParenizor.swiss(NumberValue, 'setValue', 'setRange');

This adds only the requested methods to our class.

Parasitic Inheritance

There is another way to write ZParenizor. Instead of inheriting from Parenizor, we write a constructor that calls the Parenizor constructor, passing off the result as its own. And instead of adding public methods, the constructor adds privileged methods.

function ZParenizor2(value) {
    var that = new Parenizor(value);
    that.toString = function () {
        if (this.getValue()) {
            return this.uber('toString');
        return "-0-"
    return that;

Classical inheritance is about the is-a relationship, and parasitic inheritance is about the was-a-but-now's-a relationship. The constructor has a larger role in the construction of the object. Notice that the uber née super method is still available to the privileged methods.

Class Augmentation

JavaScript's dynamism allows us to add or replace methods of an existing class. We can call the method method at any time, and all present and future instances of the class will have that method. We can literally extend a class at any time. Inheritance works retroactively. We call this Class Augmentation to avoid confusion with Java's extends, which means something else.

Object Augmentation

In the static object-oriented languages, if you want an object which is slightly different than another object, you need to define a new class. In JavaScript, you can add methods to individual objects without the need for additional classes. This has enormous power because you can write far fewer classes and the classes you do write can be much simpler. Recall that JavaScript objects are like hashtables. You can add new values at any time. If the value is a function, then it becomes a method.

So in the example above, I didn't need a ZParenizor class at all. I could have simply modified my instance.

myParenizor = new Parenizor(0);
myParenizor.toString = function () {
    if (this.getValue()) {
        return this.uber('toString');
    return "-0-";
myString = myParenizor.toString();

We added a toString method to our myParenizor instance without using any form of inheritance. We can evolve individual instances because the language is class-free.


To make the examples above work, I wrote four sugar methods. First, the method method, which adds an instance method to a class.

Function.prototype.method = function (name, func) {
    this.prototype[name] = func;
    return this;

This adds a public method to the Function.prototype, so all functions get it by Class Augmentation. It takes a name and a function, and adds them to a function's prototype object.

It returns this. When I write a method that doesn't need to return a value, I usually have it return this. It allows for a cascade-style of programming.

Next comes the inherits method, which indicates that one class inherits from another. It should be called after both classes are defined, but before the inheriting class's methods are added.

Function.method('inherits', function (parent) {
    this.prototype = new parent();
    var d = {}, 
        p = this.prototype;
    this.prototype.constructor = parent; 
    this.method('uber', function uber(name) {
        if (!(name in d)) {
            d[name] = 0;
        var f, r, t = d[name], v = parent.prototype;
        if (t) {
            while (t) {
                v = v.constructor.prototype;
                t -= 1;
            f = v[name];
        } else {
            f = p[name];
            if (f == this[name]) {
                f = v[name];
        d[name] += 1;
        r = f.apply(this, Array.prototype.slice.apply(arguments, [1]));
        d[name] -= 1;
        return r;
    return this;

Again, we augment Function. We make an instance of the parent class and use it as the new prototype. We also correct the constructor field, and we add the uber method to the prototype as well.

The uber method looks for the named method in its own prototype. This is the function to invoke in the case of Parasitic Inheritance or Object Augmentation. If we are doing Classical Inheritance, then we need to find the function in the parent's prototype. The return statement uses the function's apply method to invoke the function, explicitly setting this and passing an array of parameters. The parameters (if any) are obtained from the arguments array. Unfortunately, the arguments array is not a true array, so we have to use apply again to invoke the array slice method.

Finally, the swiss method.

Function.method('swiss', function (parent) {
    for (var i = 1; i < arguments.length; i += 1) {
        var name = arguments[i];
        this.prototype[name] = parent.prototype[name];
    return this;

The swiss method loops through the arguments. For each name, it copies a member from the parent's prototype to the new class's prototype.