JS programowanie obiektowe. 1. JavaScript Programowanie Obiektowe Piotr Czajkowski [email protected]; 2. constructor new. Poznasz i zrozumiesz najnowsze mechanizmy JS (ES6+) Programowanie obiektowe z użyciem słów kluczowych class, extends itd. In the early nineties, a thing called object-oriented programming stirred up the software industry. Most of the ideas behind it were not really new at the time, but.

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You could try to make the lichen-eater-eaters ‘hibernate’ use the “wait” action for a whilewhen they fail to find food for a few turns. The name javacsript.programowanie or that is often used for such a variable.

We are interested only in the properties that the object javascript.provramowanie has. Unfortunately, none of them is oniektowe perfect. Quite a few times, I have found myself accidentally adding methods to a constructor instead of its prototype, or trying to call Array. These three functions form an interface for such objects. In an object-oriented approach, objects are viewed as little worlds of their own, and the outside jafascript.programowanie may touch them only through a limited and well-defined interface, a number of specific methods and properties.

Then, if the action has a direction property, it immediately computes which point on the grid this direction points to and which value is currently sitting there. It has four methods: If we make the old prototype object the prototype of the new prototype object you may have to re-read that a few timesit will automatically have all its properties. JavaScript does not, so you will have to rely on comments to describe the interface to an object. In this case there is not much harm done, but there are situations where this would cause a problem.

It will be stored in the object, and the next time we javacript.programowanie to go over the collection of cats, calling object.

Why would piano[0] give me the first key, and not the first pedal? To prevent wasting your time, it is advisable to document your interfaces only after they have been used in a few real situations and proven themselves to be practical. All of a sudden, everybody was extolling the virtues of object-orientation, enthusiastically applying it to every problem, convincing themselves obietowe had finally found the right way to write programs.


Every object has a method called hasOwnPropertywhich tells us whether the object has a property with a given name. In this new approach to prototypes, types that need no constructor can leave it out. Javascript.programowanie way, objects of the new type can be polymorphically used in all the places where objects of the old type could be used.

It would be nicer if it would print automatically. This technique is called ‘ inheritance’. We had to write an empty, useless constructor for StrangeArray in javascriptprogramowanie example above. It returns a function like print which, instead of adding to the output, replaces its previous output.

JavaScript. Programowanie obiektowe by Stoyan Stefanov on Apple Books

It is possible to write a function that does this, though, by using the following trick:. For most actions, the action also contains extra information, such as the direction the bug wants to go. This way, it starts with a valid object of the super-type, which it can then extend. Otherwise, if there is space to move, it moves into a random nearby empty square. It clones the object, and calls its construct method, if there is such a method, giving it the arguments that were passed to create.

That is not very practical.

Sure, duplicating the line is shorter than calling the Item. The trick of only eating when it spots two pieces of food doesn’t work very well for them, because their food moves around so much it is rare to find two in one place.

We will take a rather simple approach, and make the terrarium a two-dimensional grid, like the second map in chapter 7. They will automatically inherit the constructor of their super-type.

Try to find a way to javascript.programowanid it fit in the ecosystem without dying out too quickly. So far, we have used objects as loose aggregations of values, adding and altering their properties whenever we saw fit.


We could put it into a function, but an even better approach is to write a constructor and a prototype specifically for situations like this, where we want to approach an object as just a set of properties. For now, it only knows about the “move” action: But I guess that can wait until we need it. SmallItem can be seen as such a prototype. When something looking like such a solution presents itself, they are prepared to become devoted followers.

Constructors take javascriptt.programowanie very central role, they are the things that give an object type obifktowe name, and when you need to get at a prototype, you have to go to the constructor and take its prototype property. By making them only eat if they see at least two lichen nearby, no matter how hungry they are, they will never exterminate the lichen.

It starts with an energy of 10and behaves in the following way:.

JavaScript Programowanie obiektowe : Stoyan Stefanov :

Books were being written, courses given, programming languages developed. It is possible to write a function that does this, though, by using the following trick: Can you write a new creature, LichenEaterEater character ” “which survives by eating lichen-eaters?

One can use an array of arrays, like this:. For example, if SmallItem would, for some reason, also define an inspect method, which inspect method should the new prototype use? For many programmers, even today, object-orientation or their view of it is the gospel. The sub-type starts with all the properties and methods of the super-type, it inherits them, and then modifies a few of these, and optionally adds new ones.

JavaScript Programowanie obiektowe

This requires some discipline, but the result is a biotope that does not destroy itself. Give the lichen-eater “c” as its character pac-man. JavaScript does not allow an object to have multiple prototypes, and even if it did, the problem would not be quite that easy to solve.