function Polygon(sides) {
this.sides = sides;
}
Polygon.prototype.getArea = function() {
return 0;
}
function Triangle(base, height) {
Polygon.call(this, 3);
this.base = base;
this.height = height;
}
Triangle.prototype = new Polygon();
Triangle.prototype.getArea = function() {
return 0.5 * this.base * this.height;
}
function Rectangle(length, width) {
Polygon.call(this, 4);
this.length = length;
this.width = width;
}
Rectangle.prototype = new Polygon();
Rectangle.prototype.getArea = function() {
return this.length * this.width;
}
function Square(length) {
Rectangle.call(this, length);
}
Square.prototype = new Rectangle();
Square.prototype.getArea = function() {
return this.length * this.length;
}
function main() {
var polygon = new Polygon(0);
alert("Polygon " + polygon.sides + " area:" + polygon.getArea());
var triangle = new Triangle(4, 4);
alert("Triangle " + triangle.sides + " area:" + triangle.getArea());
var rectangle = new Rectangle(4, 5);
alert("Rectangle " + rectangle.sides + " area:" + rectangle.getArea());
var square = new Square(4);
alert("Square " + square.sides + " area:" + square.getArea());
alert("Triangle is a kind of Polygon - " + (triangle instanceof Polygon));
alert("Rectangle is a kind of Polygon - " + (rectangle instanceof Polygon));
alert("Square is a kind of Polygon - " + (square instanceof Polygon));
alert("Square is a kind of Rectangle - " + (square instanceof Rectangle));
alert("Square is a kind of Triangle - " + (square instanceof Triangle));
alert("Rectangle is a kind of Triangle - " + (rectangle instanceof Triangle));
}
使用了zInherit库可以实现多重继承
function ClassA(color) {
this.color = color;
}
ClassA.prototype.sayColor = function () {
alert(this.color);
}
function ClassB(size) {
this.size = size;
}
ClassB.prototype.saySize = function () {
alert(this.size);
}
function ClassC(color, size, font) {
ClassA.call(this, color);
ClassB.call(this, size);
this.font = font;
}
ClassC.prototype.inheritFrom(ClassA);
ClassC.prototype.inheritFrom(ClassB);
ClassC.prototype.sayFont = function() {
alert(this.font);
}
function main() {
var objc = new ClassC('blue', 12, 'sans');
objc.sayColor();
objc.saySize();
objc.sayFont();
alert(objc.instanceOf(ClassA));
alert(objc.instanceOf(ClassB));
alert(objc.instanceOf(ClassC));
}
用xbObjects（http://archive.bclary.com/xbProjects-docs/xbObject）可以给JavaScript提供了继承，方法重载和调用超类的方法的能力

_classes.registerClass("Polygon");
function Polygon(sides) {
_classes.defineClass("Polygon", prototypeFunction);
this.init(sides);
function prototypeFunction() {
Polygon.prototype.init = function(sides) {
this.parentMethod("init");
this.sides = sides;
}
Polygon.prototype.getArea = function() {
return 0;
}
}
}
_classes.registerClass("Triangle", "Polygon");
function Triangle(base, height) {
_classes.defineClass("Triangle", prototypeFunction);
this.init(base, height);
function prototypeFunction() {
Triangle.prototype.init = function(base, height) {
this.parentMethod("init", 3);
this.base = base;
this.height = height;
}
Triangle.prototype.getArea = function() {
return 0.5 * this.base * this.height;
}
}
}
_classes.registerClass("Rectangle", "Polygon");
function Rectangle(length, width) {
_classes.defineClass("Rectangle", prototypeFunction);
this.init(length, width);
function prototypeFunction() {
Rectangle.prototype.init = function(length, width) {
this.parentMethod("init", 4);
this.length = length;
this.width = width;
}
Rectangle.prototype.getArea = function() {
return this.length * this.width;
}
}
}
_classes.registerClass("Square", "Rectangle");
function Square(length, width) {
_classes.defineClass("Square", prototypeFunction);
this.init(length);
function prototypeFunction() {
Square.prototype.init = function(length, width) {
this.parentMethod("init");
this.length = length;
this.width = width;
}
Square.prototype.getArea = function() {
return this.length * this.length;
}
}
}
function main() {
var polygon = new Polygon(0);
alert("Polygon " + polygon.sides + " area:" + polygon.getArea());
var triangle = new Triangle(4, 4);
alert("Triangle " + triangle.sides + " area:" + triangle.getArea());
var rectangle = new Rectangle(4, 5);
alert("Rectangle " + rectangle.sides + " area:" + rectangle.getArea());
var square = new Square(4);
alert("Square " + square.sides + " area:" + square.getArea());
alert("Triangle is a kind of Polygon - " + (triangle.isInstanceOf(Polygon)));
alert("Rectangle is a kind of Polygon - " + (rectangle.isInstanceOf(Polygon)));
alert("Square is a kind of Polygon - " + (square.isInstanceOf(Polygon)));
alert("Square is a kind of Rectangle - " + (square.isInstanceOf(Rectangle)));
alert("Square is a kind of Triangle - " + (square.isInstanceOf(Triangle)));
alert("Rectangle is a kind of Triangle - " + (rectangle.isInstanceOf(Triangle)));
}