Trying to get Area, and Volume of a Cylinder

**RustyC** · 05-09-2012 11:08 AM

I am having trouble trying to get the following to work. It will pass the radius, but not the height. Any help you can be would be greately appreciated,

<html>
<head>
<script>

function Cylinder(radius) {

this.radius = radius;
this.volume = volume;

this.surface_area = surface_area;
//this.height = height;

alert("radius1: " + this.radius);
// alert("radius: " + radius);

}

function Cylheight(height){
this.height = height;

//return height;

// alert("hight: " + this.height);
}

function volume() {

var volume = Math.PI * (this.radius * this.radius) * this.height;
alert("radius1: " + this.radius);
alert("hight1: " + this.height);
return volume;

}

function surface_area() {

var surface_area = (Math.PI * 2) * (this.radius * this.radius) + (Math.PI * 2) * this.radius * this.height ;

alert("radius2: " + this.radius);
return surface_area;

}

</script>

</head>

<body>

<h1>Volume, and Surface Area</h1>

<script>

var rad = parseInt(prompt("Enter the radius of the cylinder: "));
var hgt = parseInt(prompt("Enter the height of the cylinder: "));
var myCylinder = new Cylinder(rad);
var myCylheight = new Cylheight(hgt);
alert("The cylinder's volume is " + myCylinder.volume() + " units");
alert("The cylinder's Surface Area is " + myCylinder.surface_area() + " units");
</script>
</body>
</html>

**RustyC** · 05-09-2012 12:23 PM

I am getting undefined for the height,

**TheAliveWinner** · 05-09-2012 12:54 PM

After spending around 15 mins to debug your code,
I was only able to make out that your code is a total mess!

The only possible solution to me is to re-code your code!

**coothead** · 05-09-2012 01:24 PM

Hi there RustyC,

and a warm welcome to these forums.

Try it like this...

Code:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
   "http://www.w3.org/TR/html4/strict.dtd">
<html lang="en">
<head>

<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<meta name="language" content="english"> 
<meta http-equiv="Content-Style-Type" content="text/css">
<meta http-equiv="Content-Script-Type" content="text/javascript">

<title></title>

<script type="text/javascript">

function init(){

   var rad,hgt;

while(isNaN(rad)) {
   rad=parseFloat(prompt('Enter the radius of the cylinder: '));
if(isNaN(rad))   {
   alert('Please enter a number');
  }
 }

while(isNaN(hgt)) {
   hgt=parseFloat(prompt('Enter the height of the cylinder: '))
if(isNaN(hgt))   {
   alert('Please enter a number');
  }
 }

   area=2*Math.PI*rad*(rad+hgt);
   volume=Math.PI*rad*rad*hgt;

document.getElementById('result').innerHTML=
   'The cylinder\'s Surface Area is '+area.toFixed(2)+' square units.<br>'+
   'The cylinder\'s volume is '+volume.toFixed(2)+' cubic units.';
 }

   window.addEventListener?
   window.addEventListener('load',init,false):
   window.attachEvent('onload',init);

</script>

</head>
<body>

<h1>Volume, and Surface Area</h1>

<div id="result"></div>

</body>
</html>

coothead

**RustyC** · 05-09-2012 01:45 PM

Thanks Coothead, As you can tell I am new to Javascript. I appreciate you taking the time to help.

Rusty

**coothead** · 05-09-2012 01:53 PM

No problem, you're very welcome.

coothead

**mrhoo** · 05-09-2012 01:56 PM

Another way, using the constructor-

Code:

<html>
<head>
</head>
<body>
<h1>Volume, and Surface Area</h1>
<script>
function Cylinder(r,h){
    this.radius= r;
    this.height= h;
}
Cylinder.prototype.getVolume=function(){
    var r= this.radius, h= this.height, pi= Math.PI;
    return pi*r*r*h;
}
Cylinder.prototype.getSurface=function(){
    var r= this.radius, h= this.height, pi2= Math.PI*2;
    return  pi2*r*r+ pi2*r*h;
}
var rad= parseInt(prompt("Enter the radius of the cylinder: ",""));
var hgt= parseInt(prompt("Enter the height of the cylinder: ",""));
var units= ' units';
var c1=new Cylinder(rad,hgt);
alert("The volume is " + c1.getVolume().toFixed(4)+ 
" cubic "+units+"\nThe  Surface Area is " + c1.getSurface().toFixed(4)+" square "+units);
</script>
</body>
</html>

**RustyC** · 05-09-2012 02:14 PM

Thanks Mrhoo. I appreciate the help.

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