wildlifeprotection.info Laws The Principles Of Object-oriented Javascript Pdf


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Zakas, Nicholas C. The principles of object-oriented JavaScript / by Nicholas C. Zakas. pages cm. Includes index. ISBN (paperback). If you've used a more traditional object-oriented language, such as C++ or Java, JavaScript probably doesn't seem object-oriented at all. It has no concept of. Download Chapter 3: "Understanding Objects" (PDF). If you've used a more traditional object-oriented language, such as C++ or Java, JavaScript probably.

The Principles Of Object-oriented Javascript Pdf

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Download Chapter 3: "Understanding Objects" (PDF). If you've used a In The Principles of ObjectOriented JavaScript, Nicholas C. Zakas thoroughly explores. Contribute to Javis/T-i-li-u-javascript development by creating an account on GitHub. NET developers are familiar with the fundamental OOP principles because this downloaded in PDF format at wildlifeprotection.info To ensure.

This turned out to be a terrible idea -- it meant that JavaScript was renamed, and rewritten to mimic a lot of Java syntax, and, as a result, it cau JavaScript is a rather strange language. This turned out to be a terrible idea -- it meant that JavaScript was renamed, and rewritten to mimic a lot of Java syntax, and, as a result, it caused a huge amount of confusion because it looked like Java while in fact being a very different language.

The languages use totally different models.

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People are still confused by that today, 20 years later. Add to JavaScript's oddities the fact that, while there are a lot of JavaScript books, most of them seem to concentrate on Java as a procedural language, and there was and still is a lot of emphasis on "learning" JavaScript by cutting and pasting other people's code, without understanding the fundamentals of the language. This produced some really bad practices.

Then, there is the fact that JavaScript is used almost but not completely exclusively in Web browsers, and so you have to not only know the language but also understand how it fits in the web browser context, and learn about additional JavaScript objects such as Document and Window, and the like -- the so-called DOM Document Object Model , which is so important when dealing with web pages and JavaScript.

This adds enormous complexity to a misleadingly "simple" language.

Some time ago, I was teaching a course in Web Development, and tried to teach JavaScript by teaching good practices, and I tried to explain and use!

JavaScript's oft-touted object-orientation. Java is a class-based object-oriented programming language.

On the other hand JavaScript does not have classes; it uses what is referred to as prototype-based object orientation. At the time I was researching and teaching the course, I found precious few resources to help me with those aspects of JavaScript.

This was exacerbated by the fact that Netscape was using their own, original, version, while Microsoft had reverse engineered JavaScript and came up with their own version, JScript. Inevitably, there were incompatibilities that made the problems far worse.

So I never finished my goal of teaching JavaScript to the level of how to use it object-orientation -- at least, to my satisfaction. This book would undoubtedly have helped me in that long-ago quest. It is the first book I've seen that deals explicitly with the JavaScript object model, and it does so in a reasonable way.

If either inheritance or composition can reasonably express our program concepts and relationships, then prefer composition. Inherit to Substitute Subclasses Inheritance also allows different subclasses to be used interchangeably through the interface provided by a common superclass.

A function that expects a superclass instance as an argument can also be passed a subclass instance without the function having to know about any of the subclasses. We faked inheritance of static properties by manually copying them.

Arrays, for example, adjust their length property to be greater than the largest integer index. In ES5, objects were allocated before invoking the subclass constructor, and the subclass would pass that object to the superclass constructor. Now with ES6 classes, objects are allocated before invoking the superclass constructor, and the superclass makes that object available to the subclass constructor. This lets Array allocate an exotic object even when we invoke new on our subclass.

This protects against forgetting to invoke constructors with new. This may help JavaScript engines optimize class objects. This may save memory by eliminating unnecessary objects.

Constructors and object instances

Using New Features in Imaginative Ways Many of the features described here and in other SitePoint articles are new to JavaScript, and the community is experimenting right now to use those features in new and imaginative ways. Multiple Inheritance with Proxies One such experiment uses proxies , a new feature to JavaScript for implementing multiple inheritance.

Objects can delegate to only one other object. The JavaScript community is working on this right now. Can you figure it out?

Join the discussion and share your ideas. Multiple Inheritance with Class Factories Another approach the JavaScript community has been experimenting with is generating classes on demand that extend a variable superclass.

Conclusion As the graphic below shows, support for classes is pretty good. Can I Use es6-class?

The Principles of Object-Oriented JavaScript

Data on support for the es6-class feature across the major browsers from caniuse. Here we'll look at OOP theory in general, not in the context of any specific programming language. To start this off, we could return to our Person object type from our first objects article , which defines the generic data and functionality of a person. There are lots of things you could know about a person their address, height, shoe size, DNA profile, passport number, significant personality traits This is known as abstraction — creating a simple model of a more complex thing, which represents its most important aspects in a way that is easy to work with for our program's purposes.

Creating actual objects From our class, we can create object instances — objects that contain the data and functionality defined in the class.

From our Person class, we can now create some actual people: When an object instance is created from a class, the class's constructor function is run to create it.

This process of creating an object instance from a class is called instantiation — the object instance is instantiated from the class. Specialist classes In this case we don't want generic people — we want teachers and students, which are both more specific types of people. In OOP, we can create new classes based on other classes — these new child classes can be made to inherit the data and code features of their parent class, so you can reuse functionality common to all the object types rather than having to duplicate it.

Where functionality differs between classes, you can define specialized features directly on them as needed. This is really useful — teachers and students share many common features such as name, gender, and age, so it is convenient to only have to define those features once.

You can also define the same feature separately in different classes, as each definition of that feature will be in a different namespace. For example, a student's greeting might be of the form "Yo, I'm [firstName]" e.

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Note: The fancy word for the ability of multiple object types to implement the same functionality is polymorphism. Just in case you were wondering. You can now create object instances from your child classes.

For example: In the rest of the article, we'll start to look at how OOP theory can be put into practice in JavaScript. They are useful because you'll often come across situations in which you don't know how many objects you will be creating; constructors provide the means to create as many objects as you need in an effective way, attaching data and functions to them as required.

Let's explore creating classes via constructors and creating object instances from them in JavaScript.This adds enormous complexity to a misleadingly "simple" language. For an experienced developer, it restates the obvious in an disturbingly careless manner. It has no concept of classes, and you don't even need to define any objects in order to write code.

So this post gets to act as my memory until the four principles of object-oriented programming encapsulation, inheritance, polymorphism and abstraction. It covers a lot of the features brought into ECMAScript 5 which is probably the most prevalent version available today it'll be a while before ES6 is available everywhere and thus most relevant for developers aiming to have their software work on any browser and on any platform. Another area of concern for me was the ability to update the ebook whenever I wanted.

We used this approach in the earlier code example. First of all, we'd like you to make a new local copy of the oojs. You can put any code you like inside a constructor you'll probably need a few conditionals and a loop.

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