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

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

Inheritance

Polymorphism

Encapsulation Definition Data + Operation Single logically organized unit Data visibility

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

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 )

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

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++; }

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

See Listing 1

See Listing 2

Polymorphism See Listing 1

See Listing 1

What more? JSON Closures

JSON

Closures

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

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

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