completed about prototypal inheritance

Author: liammclennan

topics/about_prototypal_inheritance.js

@@ -5,5 +5,61 @@ $(document).ready(function(){
 
 	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 beadded 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");
+		equals(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");
+		equals(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;
+		};
+		// for the following statement asks the paul object to call a function that was added to the Mammal prototype after paul was constructed.
+		equals(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.__proto__ = 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");
+		equals(lenny.sayHi(), __, "what does Lenny say?");
+		equals(lenny.wingspan, __, "what is Lenny's wingspan?");
+	});
+
 
 });