Need to add a checkbox value to totalsum

[RayTracy]

I´m trying to add a value to totalsum when checking a checkbox.
But I'm a n00b at this and I can't find any relevant information on the Internet to help me with my little problem.
I'm only including the relevant part of the script since it is way way long and the only thing that differs is the different artnr.
The + 60 in the last line is for shipping and handling so it should be left there as is.
The text in bold is what I can't get working...

I'm using JavaScript and so far the script looks like this:

<script language="JavaScript">

function calculate(){
var totalsum = 0;
if(!isNaN(parseInt(document.forms[0].artnr110.value))){
totalsum=totalsum + parseInt(document.forms[0].artnr110.value)*199;
document.forms[0].sum110.value = parseInt(document.forms[0].artnr110.value)*199;
}
if(!isNaN(parseInt(document.forms[0].extra.checked))){
totalsumma=totalsumma + parseInt(document.forms[0].extra.checked)*1;
}

document.forms[0].summa.value = totalsumma + (60) + " :-";
}
</script>

These are some values I have in my form:
<form name="order" action="order.asp" method="POST">

<INPUT TYPE="TEXT" SIZE="2" NAME="artnr110"
id="artnr110" onChange="calculate()">

<INPUT TYPE="TEXT" SIZE="2" NAME="sum110"
id=sum110 readonly>

<INPUT TYPE="TEXT" SIZE="3" NAME="sum"
id=sum width="20">

<INPUT TYPE="checkbox" NAME="extra" VALUE="50"
id=extra onClick="calculate()">

<input type="submit" value="send" name="order" />

</form>

I got everything but that checkbox to work. I tried around with different settings but beeing a n00b has it's limitations... ;)

Thanks in advance for help.
Ray

[epots9]

Hi RayTracy welcome to TSDN

in your if statement your checking to see if the checkbox was checked, so its returning a true or false and your parsing it, what u want is to get the value:

if(!isNaN(parseInt(document.forms[0].extra.value))){
totalsumma=totalsumma + parseInt(document.forms[0].extra.checked)*1;
}
 

good luck

[RayTracy]

Hi RayTracy welcome to TSDN

in your if statement your checking to see if the checkbox was checked, so its returning a true or false and your parsing it, what u want is to get the value:

if(!isNaN(parseInt(document.forms[0].extra.value))){
totalsumma=totalsumma + parseInt(document.forms[0].extra.checked)*1;
}
 

good luck

Thank you for trying to help me. Much appreciated.
However, when changing to the suggested code all of the sudden I got NaN in my totalsum. I know NaN is Not a Number, but the value of extra = 1 so how in the heck can it become NaN?

If I delete the value of extra, then the calculation is correct, however without the value I want added, ofcourse.

Any suggestions, anyone?

\\Ray