Javascript - Javascript Object
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Aralık 5, 2012 by Javascript Tutorial
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Article Information
This Javascript tutorial contains and tries to cover following subjects:
- Explanation of Javascript Objects and introduction to Object-oriented Programming in Javascript
- Example to an Javascript Objects
- Example to create a javascript object
Articles tries to provide answer to following questions and issues:
- What is object in javascript?
- How to use objects in javascript?
- Why objects are required in javascript?
Articles pre-requisites following information:
- General knowledge of Object-Oriented Programming
Javascript Object
In this Javascript Tutorial, we will cover aJavascript objects subject. To start with explanation of what is object, where and why to use them.
Javascript is an object oriented language. Object oriented means, the things we use in that language, they are object. Idea behind an object is that an object in real-life has some properties. Assume a notebook or desktop. Those both are objects. They both have a keyboard, and mouse. However, with slight differences. Desktops have a case, notebooks have not. Both of those can be restarted. To take that logic into programming, its easier to understand what an object in a programming language is.
Lets take that logic into javascript to understand what is idea behind an object in javascript. If you recall in earlier javascript tutorials that we used some javascript methods, the method "write" as "document.write()". Method "write" is an object method. There that explanation seems fuzzy about objects. However, assume that you have a web application that pulls data from database. Our web page is some sort of hardware site, and displays review about particular notebooks.
When programming such site, we can declare some variables about a notebook that refers to database fields of that notebook. For example:
var v_notebookModel;
var v_notebookID;
var v_notebookColor:
This is a usual approach without looking it with object-oriented logic. If we declare a notebook object in code, similar to real-life, and whenever we create a notebook object that it can automatically has properties for above variables, it becomes more easier to manage code. Instead declaring some variables, we declare an object notebook and its properties.
Object-oriented logic brings managable and structured system to the programming. Lets consider our scenario: Computer is an object, notebook too. While computers have ID, notebooks have ID and battery. Desktops have ID too, but they use power supply not battery. If you look as object logic, we have 3 object.
1 generic object: Computer which has only ID property
1.a notebook object: sub object of Computer with additionally battery property (has ID + battery property)
1.a desktop object: sub object of Computer with additionally power supply property (has ID + battery property)
Objects are created as an instance. In programming area, "instance" is a technical term to mean, an object that is created "as instance" of a Class. Class describes an object as template. To understand easier lets look into it step by step:
1. A class is created. Class describes template of object.
2. Another Class is described. It is made child class. Takes properties of first class, and adds some another template information.
In our scenario about hardware site:
We create a Computer Class, it is parent. Notebook is a class, it is child Class. Computer Class has one variable "ID". Notebook has one variable "batteryInfo". Computer Class has one method called "restart". Notebook has "restart" method too. Therefore, we add "restart" method to main Class.
Whenever we create an notebook object in our code, our notebook object will automatically have two property ("ID, "batteryInfo") to assign value and one method ("restart") available to use with our notebook objects.
This logic applies to entire javascript. If you recall, we had created an array. Array is an object.
However, javascript is not Class oriented like C# for example. In C#, we create a Class, add methods and properties similar to above logic. JavaScript is prototype based. It means we create a object instead. It looks similar to creation of Class.
To be more practice, lets look creating an object in example. We will be creating an employee object which can store name and age. A method also which displays salary of employee.
Example to create a Javascript Object
In following javascript example, we will create a Javascript object. Additionally, we will add properties and a method to javascript object we created.
HTML page shows result at the right pane. We created a javascript object, and named it as "employees". We added 4 property and 1 method. Finally, we displayed salary of an employee which we created as object.
Data Layers
| Area: | programming \ languages \ javascript \ \ \ |
| Ref: | |
| Loc: | articles |
| Tags: | javascript |
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