<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>JavaScript - Encapsulation Exercise</title>
</head>
<body>
<p>
<script language="JavaScript" type="text/JavaScript">
// ************************************************************************
// CREATE AN AUTOMOBILE USING A CONSTRUCTOR
// ************************************************************************
function Automobile(speed)
{
// ************************************************************************
// PUBLIC PROPERTY -- ANYONE MAY READ/WRITE
// ************************************************************************
this.model = "Standard";
// ************************************************************************
// PRIVATE VARIABLE AND FUNCTION
// ONLY PRIVELEGED METHODS MAY VIEW/EDIT/INVOKE
// ***********************************************************************
var drivingSpeed = speed;
var milePerGallonValue1 = 0;
var milePerGallonValue2 = 0;
// ************************************************************************
// PRIVILEGED METHODS
// MAY BE INVOKED PUBLICLY AND MAY ACCESS PRIVATE ITEMS
// MAY NOT BE CHANGED; MAY BE REPLACED WITH PUBLIC FLAVORS
// ************************************************************************
this.setMilePerGallonEquation = function(param1, param2)
{
milePerGallonValue1 = param1;
milePerGallonValue2 = param2;
}
this.getMilePerGallonEquation = function()
{
return milePerGallonValue1 * milePerGallonValue2;
}
this.getBaseMilesPerGallon = function()
{
return Math.round( drivingSpeed / this.getMilePerGallonEquation() );
}
this.setBaseSpeed = function(newSpeed)
{
drivingSpeed = newSpeed;
}
this.getBaseSpeed = function()
{
return drivingSpeed;
}
}
// ************************************************************************
// PROTOTYOPE PROERTIES -- ANYONE MAY READ/WRITE (but may be overridden)
// ************************************************************************
Automobile.prototype.tankSize = 13;
// ************************************************************************
// STATIC PROPERTIES -- ANYONE MAY READ/WRITE
// ************************************************************************
Automobile.opinion = "";
// ************************************************************************
// PUBLIC METHODS -- ANYONE MAY READ/WRITE
// ************************************************************************
Automobile.prototype.setIdealSpeed = function(ideal)
{
this.idealSpeed = ideal;
}
Automobile.prototype.getIdealSpeed = function()
{
return this.idealSpeed;
}
Mercedes.prototype = new Automobile();
function Mercedes(autoMobile)
{
this.setBaseSpeed( autoMobile.getBaseSpeed() );
}
Porsche.prototype = new Automobile();
function Porsche(autoMobile)
{
this.setBaseSpeed( autoMobile.getBaseSpeed() );
}
function performTest()
{
autoMobileObject = new Array(3)
autoMobileObject[0] = new Automobile(50);
autoMobileObject[1] = new Mercedes( autoMobileObject[0] );
autoMobileObject[2] = new Porsche( autoMobileObject[0] );
autoMobileObject[0].setMilePerGallonEquation(.015, 100);
autoMobileObject[1].setMilePerGallonEquation(.03, 100);
autoMobileObject[2].setMilePerGallonEquation(.02, 100);
alert("At " + autoMobileObject[0].getBaseSpeed() + " mph. the " + autoMobileObject[0].model + " version of my Automobile with a " + autoMobileObject[0].tankSize + " gallon tank will get " + autoMobileObject[0].getBaseMilesPerGallon() + " miles per gallon." );
// ******************************************************************************************************************
// CREATE A TEST TO EVALUATE THE BEST MILES PER GALLON FOR A BASIC AUTOMOBILE
// ******************************************************************************************************************
if( autoMobileObject[0].getBaseMilesPerGallon() >= 30 )
{
Automobile.opinion = "That's pretty good!";
}
else
{
Automobile.opinion = "That's not good";
}
alert( Automobile.opinion );
alert("At " + autoMobileObject[1].getBaseSpeed() + " mph. the " + autoMobileObject[1].model + " version of my Mercedes with a " + autoMobileObject[1].tankSize + " gallon tank will get " + autoMobileObject[1].getBaseMilesPerGallon() + " miles per gallon." );
// ********************************************************************************************************
// CREATE A TEST TO EVALUATE THE BEST MILES PER GALLON FOR A MERCEDES
// *********************************************************************************************************
if( autoMobileObject[1].getBaseMilesPerGallon() >= 30 )
{
Automobile.opinion = "That's pretty good!";
}
else
{
Automobile.opinion = "That's not good";
}
alert( Automobile.opinion );
alert("At " + autoMobileObject[2].getBaseSpeed() + " mph. the " + autoMobileObject[2].model + " version of my Porsche with a " + autoMobileObject[2].tankSize + " gallon tank will get " + autoMobileObject[2].getBaseMilesPerGallon() + " miles per gallon." );
// ******************************************************************************************************
// CREATE A TEST TO EVALUATE THE BEST MILES PER GALLON FOR A PORSCHE
// ******************************************************************************************************
if( autoMobileObject[0].getBaseMilesPerGallon() >= 30 )
{
Automobile.opinion = "That's pretty good!";
}
else
{
Automobile.opinion = "That's not good";
}
alert( Automobile.opinion );
// ************************************************************************************************************
// CHANGE THE IDEAL SPEED USING PUBLIC PROPERTIES AND PRIVILEGED METHODS
// ************************************************************************************************************
autoMobileObject[0].setIdealSpeed(65);
alert("For best performance the ideal speed is around " + autoMobileObject[0].getIdealSpeed() + " mph." );
autoMobileObject[0].model = "Luxury";
autoMobileObject[0].tankSize = 20;
autoMobileObject[0].setBaseSpeed(70);
alert("However, at " + autoMobileObject[0].getBaseSpeed() + " mph. the " + autoMobileObject[0].model + " version of my Automobile with a " + autoMobileObject[0].tankSize + " gallon tank will get " + autoMobileObject[0].getBaseMilesPerGallon() + " miles per gallon." );
if( autoMobileObject[0].getBaseMilesPerGallon() >= 30 )
{
Automobile.opinion = "That's pretty good!";
}
else
{
Automobile.opinion = "That's not good";
}
alert( Automobile.opinion );
}
</script>
</p>
<p align="center"><font size="+3" face="Arial, Helvetica, sans-serif">Encapsulation
Example</font></p>
<p align="center"> </p>
<form name="form1" method="post" action="">
<div align="center">
<!-- Add button to call JavaScript function -->
<input type="button" name="peformTest" value="Perform Test" onclick="javascript:performTest()">
</div>
</form>
</body>
</html>
