In JavaScript, it is possible to inherit only from one object. There can be a single JavaScript F.prototypetype]] for an object. A class can extend only one class. But, at times it can meet limiting. For example, you have a StreetSweeper class and a class Bike and intend to mix them and have StreetSweepingBicycle. In this case, you can use the concept, called…

The operator instanceof is targeted at checking whether an object belongs to a specific class. It also helps to take inheritance into account. Now, let’s use it to build a polymorphic function, which treats arguments differently depending on their type. The instanceof operator The following syntax is used for the instanceof operator: It may return true in case the object belongs…

Array, Map, and other built-in classes are extendable. In the example below, NumsArray inherits from the native Array: The most impressive thing is that built-in methods such as map, filter, and more – return new objects of literally the inherited type NumsArray. Their internal implementation applies the constructor property of the object for that. So, in the example mentioned above, it looks like this:…

One of the most complicated issues throughout the history of JavaScript is privacy. In JavaScript, it’s not tricky to make functions and variables private. But it’s not possible to make object properties private. It can become a severe problem when it comes to managing the state of an instance. No private properties mean that each code with access to…

The keyword static describes a static method for a class. So, it’s likely to assign a method to the class function and not to its “prototype”. Methods like this are generally known as static. In a class, they start with the static keyword, as follows: So, it’s the same as directly assigning it as a property: The class constructor Car is the value…

In this chapter, we will explore the class inheritance. It is a way for one class to extend another one, and allows creating new functionality on top of the existing. The “extend” Keyword Imagine that you have a class Car: Now, let’s say that you intend to create a new class MyCar. Since car are cars, the MyCar class…

Frequently it is necessary to create many objects of the same kind. As it was already noted in chapter Constructor, operator “new”, you can do it with the help of the new function. In modern JavaScript, there exists a more advanced “class” construct, introducing new features that are useful for object-oriented programming. The “class” Syntax The syntax…