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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Another good solution is to use a function similar to partial from chapter 6. Make sure you have defined the randomElement function from exercise 8. Thus, the question of whether inheritance is being used correctly boils down to the question of whether the resulting code works correctly and avoids useless repetitions. javascript.porgramowanie

JavaScript Programowanie obiektowe

Some problems are best solved by building a complex family tree of types. Each property holds a string of one character, as returned by characterFromElementindicating what the bug can see in that direction.

This is one of the not-so-well-designed aspects of JavaScript. Books were being written, courses given, programming languages developed. Constructors take a very central role, they are the things that give an object type its name, and when you need to get at a prototype, you have to go to the constructor and take its prototype property.

Unfortunately, when a program starts to make serious use of inheritance, this approach to objects quickly becomes clumsy. You have to take care not to get too inheritance-happy, though. Note that the action function is called with both the name of the property and the value it has in the object. Fortunately, this terrarium-simulator is not required to be accurate in any way, so we can get away with it. Every object has a method called hasOwnPropertywhich tells us whether the object has a property with a given name.

Because they share these traits, the terrarium can approach them in the same way. It will be stored in the object, and the next time we want to go over the collection of cats, calling object. Every object is based on a prototype, which gives it a set of inherent properties. Calling a function always results in a new this being defined inside that function, even when it is not used as a method. In chapter 7 we used three functions, pointaddPointsand samePoint to work with points.

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The name self or that is often used for such a variable.

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. This file is part of the first edition of Eloquent JavaScript.

For that second problem, this page conveniently provides a function called inPlacePrinter. It would be nice if part of this could be moved into another object, so that the terrarium object itself doesn’t get too big and complex. A trick similar to the clone function can be used to get around it: A function is called as a method when it is looked up as a property, and immediately called, as in object.

If there is no direction property, or an invalid one, it leaves the variables target and valueAtTarget undefined. It starts with an energy of 10and behaves in the following way:. Unfortunately, none of them is quite perfect. This method looks up the character associated with a constructor, and stores it in the dictionary.

Thus, any this variable outside of the function will not be visible. You give it the object on the left hand side, and a constructor on the right hand side, and it returns a javascript.progarmowanie, true if the constructor’s prototype property is the direct or indirect prototype of the object, and false otherwise. We could just replace the method of to the Terrarium prototype, but we have become very attached to the simulation of javascript.prorgamowanie bouncing and drunk bugs, and we would hate to break our old terrarium.

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It would be nicer if it would print automatically.

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. 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.

When it needs to do any ‘constructing’ work, this is done by a method called construct. You can use a constructor’s prototype property to get access to, well, their prototype: After all, we could have simply written this:.

The first is used to cause its first argument a function, or a string containing JavaScript code to be executed periodically. This will make accidental uses of properties that are not part of an object’s interface easier to spot. An expression such as this one can be used to reliably work around this: This means that all simple objects have a toString method, which converts them to a string.

This way, if we decide for some reason to use a different method for storing the values, we only have to rewrite valueAt and setValueAtand the other methods can stay untouched. For this reason, some people prefer not to touch these prototypes at all. First, its constructor, which takes a plan an array of strings as argument, and initialises its grid.

Firstly, having a small, clearly described interface makes an object easier to use.

Justyna Walkowska (Translator of JavaScript. Programowanie obiektowe)

Code which uses point objects may freely retrieve and modify x and y. Instead, I will show a very simple approach which suffices in most cases. Here is a new approach jaascript.programowanie the Rabbit constructor: