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Monday, March 24, 2008

My 5 cents about JavaScript Prototypal Inheritance

Few days ago I read an interesting post about Simple JavaScript Inheritance.
The most hilarious thing is that prototypal inheritance is truly simple, as John wrote, but there are still a lot of developers that do not probably understand perfectly them.

In this link you can find an "all in one" page about JavaScript prototypal inheritcance and classical emulation.

As I wrote at the end of that page, please do not hesitate to correct me if there is something wrong, or please ask me more details if there is something that is not so clear.

Sorry for my not perfect yet English, and have fun with JavaScript.

(happy easter too!)

5 comments:

Ipequey said...

Hey!

Thanks for the great articles! I've been following your blog for about 3 weeks now and learning a whole lot of great JavaScript programming patterns.

Thanks a lot!

Andrea Giammarchi said...

You are welcome :)

satish said...

Hi friends,
I implemented the inheritance in this manner.. Check this out...





//Defination of top superclass
function topSuperClass () {

}
//static members
topSuperClass.staticProperty = function () {
//static private members
var TSCstaticPrivateVariable = "I am static private variable of top super class";
var TSCstaticPrivateMethod = function () {
return "I am a static private method of top super class";
};
return {
//static public members
TSCstaticPublicVariable : "I am static public variable of top super class",
TSCstaticPublicMethod : function (){
return "I am a static public method of top super class";
}
};
}();


//non static members
topSuperClass.prototype.TSCnonStaticProperty = function () {
//non static private members
var TSCnonStaticPrivateVariable = "I am non static private variable of top super class";
var TSCnonStaticPrivateMethod = function () {
return "I am a non static private method of top super class";
};
return {
//non static public members
TSCnonStaticPublicVariable : "I am non static public variable of top super class",
TSCnonStaticPublicMethod : function (){
return "I am a non static public method of top super class";
}
};
}();

//Defination of superclass
function superClass () {
}
//inheritance declaration
superClass.prototype = new topSuperClass();

//static members
superClass.staticProperty = function () {
//static private members
var SCstaticPrivateVariable = "I am static private variable of super class";
var SCstaticPrivateMethod = function () {
return "I am a static private method of super class";
};
return {
//static public members
SCstaticPublicVariable : "I am static public variable of super class",
SCstaticPublicMethod : function (){
return "I am a static public method of super class";
}
};
}();

//non static members
superClass.prototype.SCnonStaticProperty = function () {
//non static private members
var SCnonStaticPrivateVariable = "I am non static private variable of super class";
var SCnonStaticPrivateMethod = function () {
return "I am a non static private method of super class";
};
return {
//non static public members
SCnonStaticPublicVariable : "I am non static public variable of super class",
SCnonStaticPublicMethod : function (){
return "I am a non static public method of super class";
}
};
}();


//Defination of subclass
function subClass () {
}
//inheritance Declaration
//subClass.prototype = new topSuperClass();
subClass.prototype = new superClass();


//static members
subClass.staticProperty = function () {
//static private members
var SBCstaticPrivateVariable = "I am static private variable of sub class";
var SBCstaticPrivateMethod = function () {
return "I am a static private method of sub class";
};
return {
//static public members
SBCstaticPublicVariable : "I am static public variable of sub class",
SBCstaticPublicMethod : function (){
return "I am a static public method of sub class";
}
};
}();

//non static members
subClass.prototype.SBCnonStaticProperty = function () {
//non static private members
var SBCnonStaticPrivateVariable = "I am non static private variable of sub class";
var SBCnonStaticprivateMethod = function () {
return "I am a non static private method of sub class";
};
return {
//non static public members
SBCnonStaticPublicVariable : "I am non static public variable of sub class",
SBCnonStaticPublicMethod : function (){
return "I am a non static public method of sub class";
}
};
}();

//Inheritence Defination
//superClass.prototype = new topSuperClass();
//subClass.prototype = new superClass();

var test = function (){
var subClassObj = new subClass();
alert(subClassObj.SBCnonStaticProperty.SBCnonStaticPublicMethod());
alert(subClass.staticProperty.SBCstaticPublicMethod());

alert(subClassObj.SCnonStaticProperty.SCnonStaticPublicMethod());
alert(superClass.staticProperty.SCstaticPublicMethod());

alert(subClassObj.TSCnonStaticProperty.TSCnonStaticPublicMethod());
alert(topSuperClass.staticProperty.TSCstaticPublicMethod());


}


Thanks & Regards,
Satish
satish@analytica-india.com

TECHHEAD said...

That's funny. The same article from John Resig is what inspired me to write about prototype inheritance in javascript also.

I even wrote a little framework called 'Proto' to make it more intuitive. I would love it if you would check it out and tell me what you think.

http://devblog.techhead.biz/2009/04/prototype-based-programming-in_04.html

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