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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This technique is called polymorphism, and it is arguably the most powerful aspect of object-oriented programming. It calls this function for every point on the grid, giving it the point object for that point as its first argument, and the value that is on the grid at that point as second argument.

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 javacsript.programowanie. 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. On the other hand, when setting the value of a property, JavaScript never goes to the prototype, but always sets the property in the object itself.

Now those were games!

JavaScript does not, so you will have to rely on comments to describe the interface to an object. It takes an object with object and point properties, as returned by listActingCreaturesas argument. By remembering the last direction it went, and preferring that direction, the eater will waste less time, and find food faster.

When the terrarium is active, all the bugs get a chance to take an action, such as moving, every half second. Consider reading the third edition instead. Try to find a way to make it fit in the ecosystem without dying out too quickly. Prototypes are a powerful, if somewhat confusing, part of the way JavaScript objects work. That is exactly what we need for the onStep property. Javvascript.programowanie there is a property that has the javasxript.programowanie we are looking for, that is the value we get.


An expression such as this one can be used to reliably work around this:. We already saw simple examples of this, like the toString method on objects. This will not work. Instead of adding arguments to a function, this one adds a this object, using the first argument to the function’s apply method: Every object has a method called hasOwnPropertywhich tells us whether the object has a property with a given name.

Adding some functions to take care of common operations can make things a little smoother. The properties of the prototype influence the object based on it, but the properties of this object never change the prototype. Unfortunately, none of them is quite perfect. Javascript.programowamie is possible to implement a decent multiple-inheritance framework in JavaScript.

The ‘reached list’ we used at the end of chapter 7 is an example of this: When using new on this constructor, it will create a new object based on the given object. When a program is not ‘truly object-oriented’, whatever that means, it is considered decidedly inferior.

Unless someone actually javascrlpt.programowanie with the method in Object. Otherwise, if there is space to move, it moves into a random nearby empty square. Unless you are very lucky, the lichen-eaters will probably still go extinct after a while, because, in a time of mass starvation, they crawl aimlessly back and forth through empty space, jvascript.programowanie of finding the lichen that is sitting just around the corner.

Here is a new approach to the Rabbit constructor:. But to see what is going on, we have to repeatedly do print terrarium javascript.progrsmowanie, or we won’t see what is going on. Unfortunately, when a program starts to make serious use of inheritance, this approach to objects javazcript.programowanie becomes clumsy.

Here is a constructor for rabbits:. In this case there is not much harm done, but there are situations where this would cause a problem. We could of course just type [“n”, jvaascript.programowanie, This can be solved by doing something even uglier: For one thing, our killerRabbit has a property called constructorwhich points at the Rabbit function that created it.


JavaScript. Programowanie obiektowe by Stoyan Stefanov on Apple Books

To make this easy, we can use a higher-order javasscript.programowanie that takes an action as its argument. The terrarium merely provides the infrastructure that asks them what to do every half second, and if they decide to move, it makes sure this happens. Instead of providing regular functions for working with the objects, they provide a way to create such objects, using the new keyword, and a number of methods and properties that provide the rest of the interface. That is not very practical.

The property indicating what is above the bug is called “n”for North, the one indicating what is above and to the right “ne”for North-East, and so on. If you are old enough, you may at javascript.porgramowanie time have played a ‘text adventure’ game, where you move through a virtual world by typing commands, and get textual descriptions of the things around you and the actions you perform.

JavaScript Programowanie obiektowe

For example, if SmallItem obieltowe, for some reason, also define an inspect method, which inspect method should the new prototype use? Add a method toString to the Terrarium prototype, which takes no arguments and returns a string that, when given to printshows a nice two-dimensional view of the terrarium. Calling a function always results in a new javascript.pgogramowanie being defined inside that function, even when it is not used as a method.

For example, a piano also has pedals.