OOP in JavaScript

OOP in JavaScript “ The World's Most Misunderstood Programming Language” Douglas Crockford

Some Myths
JavaScript is related to Java
JavaScript was developed by Sun Microsystems
JavaScript is not Object Oriented
JavaScript does not support data hiding, i.e. everything is public

OOP Concepts
Encapsulation
Inheritance
Polymorphism

Encapsulation
Definition
Data + Operation
Single logically organized unit
Data visibility

Inheritance
Definition
Parent-child relationship between classes
Child inherits Parents’ characteristics
Child can redefine existing characteristics
Child can add more characteristics

Polymorphism
Definition
Multiple functions
Share a common name
Context specific invocation
The characteristic of being able to assign a different meaning or usage to something in different contexts ( http://searchsmb.techtarget.com/sDefinition/0,,sid44_gci212803,00.html )

Encapsulation
Private variables - Can only be accessed by private functions and privileged methods
Private functions - Can only be called by privileged methods
Privileged methods - May invoked by code external to the object
Public properties - May be read/written from outside the object
Public methods - Shared methods
Prototype properties - Shared properties

Encapsulation
function Student(name)
{
var age = 0;
var checkAge = function(){ return (age > 0) ? age : false; };
this.getAge = function(){
return (checkAge()) ? age : “Age not set”;
}
this.setAge = function(_age){ age = _age; }
this.name = name;
this.constructor.prototype.updateTotal();
}
Student.prototype.total = 0;
Student.prototype.updateTotal = function(){
this.constructor.prototype.total++;
}

Inheritance
See Listing 1
See Listing 2

Polymorphism
See Listing 1

What more?
JSON
Closures

JSON
Object – { }
Array – [ ]
Separator – , :
Var students = [
{name : “abc” , age : 20} ,
{name : “xyz” , age : 21}
];

References
http://developer.mozilla.org/en/docs/Core_JavaScript_1.5_Reference
http://mckoss.com/jscript/object.htm
http://www.sitepoint.com/article/oriented-programming-1
http://www.codeproject.com/aspnet/JsOOP1.asp
http://phrogz.net/JS/Classes/OOPinJS.html
http://javascript.crockford.com/javascript.html
http://kevlindev.com/tutorials/javascript/inheritance/index.htm
http://www.dustindiaz.com/javascript-private-public-privileged/
http://developer.yahoo.com/yui/theater/
http://www.dustindiaz.com/json-for-the-masses/
http:// www.json.org /
Google + Wikipedia = Many Many more references

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OOP in JavaScript

by manugoel2003 on Sep 12, 2007

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OOP in JavaScript — Presentation Transcript