Implementation of JavaScript Object Inheritance

1. The following describes how to combine object impersonating (attributes) and prototype chain inheritance (objects):

function classa (scolor) {
This. color = scolor;
}< BR style = "line-Height: normal;">
classa. prototype. saycolor = function () {
alert (this. color);
};


function classb (scolor, sname) {
classa. call (this, scolor);
This. name = sname;
}< BR style = "line-Height: normal;">
classb. prototype = new classa ();
classb. prototype. sayname = function () {
alert (this. name);
}

// Test:
VaR B = new classb ("red", "sangkana ");
B. saycolor ();
B. sayname ();

2. Call zinherit library inheritance:

REFERENCE The zinherit. js file. The source code of the file is listed here:

Object. Prototype. inheritfrom = function (fnclass ){

Function inheritclasses (fnclass, arrclasses ){

Arrclasses. Push (fnclass );

If (typeof fnclass. _ superclasses _ = "object "){
For (VAR I = 0; I <fnclass. _ superclasses _. length; I ++ ){
Inheritclasses (fnclass. _ superclasses _ [I], arrclasses );
}
}
}

If (typeof this. constructor. _ superclasses _ = "undefined "){
This. constructor. _ superclasses _ = new array ();
}

Inheritclasses (fnclass, this. constructor. _ superclasses __);

For (prop in fnclass. Prototype ){
If (typeof fnclass. Prototype [prop] = "function "){
This [prop] = fnclass. Prototype [prop];
}
}
};

Object. Prototype. instanceof = function (func ){

If (this. constructor = func ){
Return true;
} Else if (typeof this. constructor. _ superclasses _ = "object "){
For (VAR I = 0; I <this. constructor. _ superclasses _. length; I ++ ){
If (this. constructor. _ superclasses _ [I] = func ){
Return true;
}
}
Return false;
} Else {
Return false;
}
};

Application:

Function classx (){
This. messagex = "this is the X message .";

If (typeof classx. _ initialized = "undefined "){

Classx. Prototype. saymessagex = function (){
Alert (this. messagex );
};

Classx. _ initialized = true;
}
}

Function classy (){
This. messagey = "this is the y message .";

If (typeof classy. _ initialized = "undefined "){

Classy. Prototype. saymessagey = function (){
Alert (this. messagey );
};

Classy. _ initialized = true;
}
}

Function classz (){
Classx. Apply (this );
Classy. Apply (this );
This. messagez = "this is the Z message .";

If (typeof classz. _ initialized = "undefined "){

Classz. Prototype. inheritfrom (classx );
Classz. Prototype. inheritfrom (classy );

Classz. Prototype. saymessagez = function (){
Alert (this. messagez );
};

Classz. _ initialized = true;
}
}

Test:

VaR objz = new classz ();
Objz. saymessagex ();
Objz. saymessagey ();
Objz. saymessagez ();

3. Application xbobjects Library:

<SCRIPT type = "text/JavaScript" src = "xbobjects. js"> </SCRIPT>
<SCRIPT type = "text/JavaScript">

_ Classes. registerclass ("polygon ");

Function polygon (isides ){

_ Classes. defineclass ("polygon", prototypefunction );

This. INIT (isides );

Function prototypefunction (){

Polygon. Prototype. init = function (isides ){
This. parentmethod ("init ");
This. sides = isides;
};

Polygon. Prototype. getarea = function (){
Return 0;
};

}
}

_ Classes. registerclass ("Triangle", "polygon ");

Function triangle (IBASE, iheight ){

_ Classes. defineclass ("Triangle", prototypefunction );

This. INIT (IBASE, iheight );

Function prototypefunction (){
Triangle. Prototype. init = function (IBASE, iheight ){
This. parentmethod ("init", 3 );
This. base = IBASE;
This. Height = iheight;
};

Triangle. Prototype. getarea = function (){
Return 0.5 * This. Base * This. height;
};
}

}

_ Classes. registerclass ("rectangle", "polygon ");

Function rectangle (ilength, iwidth ){

_ Classes. defineclass ("rectangle", prototypefunction );

This. INIT (ilength, iwidth );

Function prototypefunction (){
Rectangle. Prototype. init = function (ilength, iwidth ){
This. parentmethod ("init", 4 );
This. Length = ilength;
This. width = iwidth;
}

Rectangle. Prototype. getarea = function (){
Return this. length * This. width;
};

}
}

VaR triangle = New Triangle (12, 4 );
VaR rectangle = new rectangle (22, 10 );

Alert (triangle. sides );
Alert (triangle. getarea ());

Alert (rectangle. sides );
Alert (rectangle. getarea ());

</SCRIPT>

Note:

1. zinherit Database: http://www.nczonline.net/downloads

2. xbobjects Library: http://archive.bclary.com/xbProjects-docs/xbObject/