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The languages use totally different models.
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This adds enormous complexity to a misleadingly "simple" language.
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.
Constructors and object instances
Conclusion As the graphic below shows, support for classes is pretty good. Can I Use es6-class?
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.
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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