// demonstrate the effect of modifying an objects prototype before and after the object is constructed

module("About Prototypal Inheritance (topics/about_prototypal_inheritance.js)");

// this 'class' pattern defines a class by its constructor

var Mammal = function(name) {

this.name = name;

}

// things that don't need to be set in the constructor should be added to the constructor's prototype property.

Mammal.prototype = {

sayHi: function() {

return "Hello, my name is " + this.name;

}

}

test("defining a 'class'", function() {

var eric = new Mammal("Eric");

equal(__, eric.sayHi(), 'what will Eric say?');

});

// add another function to the Mammal 'type' that uses the sayHi function

Mammal.prototype.favouriteSaying = function() {

return this.name + "'s favourite saying is " + this.sayHi();

}

test("more functions", function() {

var bobby = new Mammal("Bobby");

equal(__, bobby.favouriteSaying(), "what is Bobby's favourite saying?");

});

test("calling functions added to a prototype after an object was created", function() {

var paul = new Mammal("Paul");

Mammal.prototype.numberOfLettersInName = function() {

return this.name.length;

};

// the following statement asks the paul object to call a function that was added

// to the Mammal prototype after paul was constructed.

equal(__, paul.numberOfLettersInName(), "how long is Paul's name?");

});

// helper function for inheritance.

// From https://developer.mozilla.org/en/JavaScript/Guide/Inheritance_Revisited

function extend(child, supertype){

child.prototype = supertype.prototype;

}

// "Subclass" Mammal

function Bat(name, wingspan) {

Mammal.call(this, name);

this.wingspan = wingspan;

}

// configure inheritance

extend(Bat, Mammal);

test("Inheritance", function() {

var lenny = new Bat("Lenny", "1.5m");

equal(__, lenny.sayHi(), "what does Lenny say?");

equal(__, lenny.wingspan, "what is Lenny's wingspan?");

});