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Summary

Rectangle.prototype.getArea = function () {

return this.length * this.width;

};

}

The main difference between this and the

Triangle

class (aside from the different

registerClass()

and

defineClass()

calls) is calling the superclass

init()

method with an argument of

. Other than

that, the additional

length

and

width

properties are added and the

getArea()

method is overridden.

Summary

This chapter introduced the concept of object inheritance in ECMAScript (and, therefore, in JavaScript)

using object masquerading and prototype chaining. You learned that using these methods together is the

optimal way to establish inheritance between classes.

Finally, a couple of alternate methods of establishing inheritance were introduced: zInherit and xbObjects.

These JavaScript libraries, available free on the Internet, introduce new and different capabilities for object

inheritance.

This wraps up the discussion of ECMAScript, the core of JavaScript. The following chapters build upon

this base and introduce you to more Web-specific aspects of the language.

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Chapter 4

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