![]() Encapsulation: values are scoped to the specific object.Communication with an object is done by message passing. Because objects operate independently, they are encapsulated into modules which contain both local environments and methods. In OOP, real-world objects are each viewed as seperate entities having their own state which is modified only by built-in procedures, called methods. (Functional and procedural programming are beyond the scope of this lesson.) Object Oriented Programming (OOP) will be our primary focus for this lesson - which is an approach that structures your code around objects rather than functions and procedures. You can read more about the differences in these paradigms here. Behaviors (stuff a program can do to/with that data).In all programs, there are two primary components: JavaScript is considered a multi-paradigm language that allows you to freely mix and match object-oriented, procedural, and functional paradigms. Create an object literal based on this sentence: This school is a non-profit, in a basement, that opens at 9 and closes at 5.Ī programming paradigm is a “style” or way of thinking about and approaching problems.What might be a benefit of placing methods inside of objects (as opposed to defining them as functions outside of objects)?.this keyword that references the current context (or owner) of the code being executed.Coupling The level of connectedness between two objects.Encapsulation Hiding the details of how an object works & grouping data and behavior.Instance One specific copy of an object.Class A blueprint or template of an object that describes what information it should contain and how it should interact with the data.Constructor Function A special function for reliably creating multiple.Object A data structure of key value pairs that groups related data and behavior.Programming paradigm A style or way of thinking about and approaching programming problems. ![]() Understand and describe what this is in JavaScript.Describe how classes allow us to reuse code and create encapsulation.The classes in JavaScript become more and more convenient to use.OOP I: Making Objects with Constructor Functions and Classes The private fields and methods names must begin with #. To take advantage of encapsulation, make the fields and methods private to hide the internal details of your classes. super keyword is used to access the parent class from a child class. Inheritance is achieved using extends keyword: you can easily create a child class from a parent. You can attach fields and methods even on the class itself using the static keyword. JavaScript classes initialize instances with constructors, define fields and methods. Public and private static fields and private static methods are part of Class static features proposal.Private instance methods and accessors are part of Class private methods proposal.Public and private instance fields are part of Class fields proposal.The class features presented in this post are spread across ES2015 and proposals at stage 3.Īt the end of 2019, the class features are split between: The class syntax is way easier to work if you're familiar with the classic inheritance mechanism of Java or Swift languages.Īnyways, even if you use class syntax in JavaScript, I recommend you to have a good grasp of prototypal inheritance. Let's make sure that the field #name can be set once at the instance initialization: The prefix # must be kept every time you work with the field: declare it, read it, or modify it. Prefix the field name with the special symbol # to make it private, e.g. The private fields are accessible only within the body of the class. The outside world of the class cannot change private fields directly. These are the fields that can be read and change only within the class they belong to. Someone that uses an encapsulated class depends only on the public interface that the class provides, and doesn't couple to the implementation details of the class.Ĭlasses organized with encapsulation in mind are easier to update when implementation details change.Ī good way to hide internal data of an object is to use the private fields. 3.2 Private instance fieldsĮncapsulation is an important concept that lets you hide the internal details of a class. You can read and assign values to public fields inside the constructor, methods, and outside of the class. There's no restriction on access or update of the public fields. Name = 'Unknown' inside the class body declares a field name and initializes it with value 'Unknown'.
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