Lesson 14 - Static members in JavaScript

In the previous lesson, Object Properties in JavaScript - Accessor Descriptors, we finished object properties. Today we're going to focus on the concept of static members. Until now, we only used data, states, being carried by an instance. Properties, which we've defined, belonged to an instance and were unique to each instance. OOP, however, allows us to declare properties and methods on a class itself. We call these members static, sometimes called class members, who are independent of an instance.

WARNING! Today's lesson will show you that static members are approaches that actually violate the object-oriented principles. OOP includes them only for special cases and in general everything can be written without static members. We always have to think carefully before adding static members. Generally, I would recommend for you not to use static members ever, unless you're absolutely sure what you're doing. Like global variables, static members are something that enable you to write bad code and violate good practices. Today, we'll go over this topic just to make you understand. Use this knowledge wisely, there will be less evil in the world.

Static Properties

We can declare various elements as static, let's start with properties. As I mentioned in the introduction, static elements belong to a class, not to an instance. So the data stored there can be read even if an instance of the class has not been declared. Basically, we could say that static properties are shared among all class instances, but even that wouldn't be accurate since they aren't actually related to instances.

Let's create a new folder (e.g. static/) and create a simple User class:

...End of the preview...
Continue further