JS Function Returning undefined number

[McMaster]

Hi!

 

I have a javascript function that loops through certain elements on a page and add's the elements up.

 

For example, element 1 value is 20 and element 2 value is 10. The alert in the loop should be showing 20 and then 10, but it just shows undefined20.00 and the stops?

 

Here is my function...

		function updatePrice(couponPrice,couponQuanity,whichPrice,howMany) {
			var price = couponPrice * couponQuanity;
			var x;
			var ptotal;

			var myItems = new Array();

			document.getElementById(whichPrice).innerHTML=price.toFixed(2);

			for (x=1;x<howMany+1;x++) { 
				myItems[x] = document.getElementById('totalPrice' + x).innerHTML;

				ptotal+=myItems[x];
				alert(ptotal);

			}


		}

[.josh]

So one thing I see wrong is you have this:

 

var ptotal;

// stuff

myItems[x] = document.getElementById('totalPrice' + x).innerHTML;
ptotal+=myItems[x];

Okay so first you declare ptotal but don't assign anything to it, so even though it's declared, it's undefined. then you attempt to add add myItems[x] to it, which is a string type value, because .innerHTML is a string type value. So javascript stringifies the typeof ptotal (which is 'undefined') and uses the + operator in the context of string concatenation to concatenate the string value of what's in that element's innerHTML.

 

To fix this, you need to initialize ptotal as a number type, by assigning a value to it:

 

var ptotal=0;

Then, you need to convert the value of myItems[x] to a number type, before adding it to ptotal:

 

myItems[x] = document.getElementById('totalPrice' + x).innerHTML;
ptotal+=Number(myItems[x]);

Beyond that, since you are saying you are only getting an alert of "undefined20.00", to me that means that you have a mis-alignment of your html element id names vs. array index vs. that howMany value. Which means basically your loop isn't looping through all of your html elements. I can't really confirm this without seeing more code, like your actual html elements and what value howMany actually is, etc..

[McMaster]

Josh!

 

Thank you very much That worked a treat for me. Appreciate that.