Object oriented programming
- 2. • Object-oriented programming (OOP) uses “objects”– data structures consisting of datafields and methods and their interactions to design applications and computer programs • Each object can be seen as a tiny machine which is responsible for the set of task assign to it.
- 3. • Today, many popular programming languages (such as Java, JavaScript, C#, C++, Python, PHP etc) support object-oriented programming (OOP). • JavaScript has strong object-oriented programming capabilities. Although there is differences in object-oriented capability of javascript compared to other languages.
- 4. Terminology
- 5. • Class: Defines the characteristics of the Object. Constructor: A method called at the moment of instantiation. Object: An Instance of a Class. Method: An Object capability as walk. Property: An Object characteristic, such as color. Inheritance: A Class can inherit characteristics from another Class.
- 6. • Encapsulation: A Class defines only the characteristics of the Object, a method defines only how the method executes. Abstraction: The conjunction of complex inheritance, methods, properties of an Object must be able to simulate a reality model. Polymorphism: Different Classes might define the same method or property.
- 8. The Class in JavaScript • Unlike Java, C++ etc., JavaScript does not contains class statement. JavaScript is a prototype-based language. JavaScript uses functions as classes. Defining a class is as easy as defining a function. In the example below we define a new class called Car.
- 9. The Object (Class Instance) in JavaScript • For creating instances of any class i.e. objects use new keyword. For example, in below code snippet we created two instances of class Car.
- 10. Constructor • Constructor is a method that is used to initiate the properties of any class instance. • Thus the constructor gets called when the class is instantiated. • As in JavaScript there is no class keyword and the function serves as class definition, there is no need of defining constructor explicitly. The function defined for the class acts as constructor.
- 11. • For example, in following code snippet we have called an alert statement when class Car is instantiated.
- 12. Property (Class Instance) in JavaScript • Properties are the variable that are member of an object and can define the state of any instance of Class. Property of a class can be accessed within the class using this keyword. For example, in following code snippet we have assign a property speed to Car.
- 14. • One thing we should note here is that for inheritance works correctly, the Properties should be set in the prototype property of the class (function). The above example becomes:
- 16. Methods • To define methods in a Class, all you have to do is just define a attribute and assign an function to it. For example, in below code snippet we defined a method setSpeed() for class Car.
- 18. Inheritance in JavaScript • JavaScript supports single class inheritance. To create a child class that inherit parent class, we create a Parent class object and assign it to the Child class. In following example we created a child class Ferrari from parent class Car.