Why doesn't this work?? (Adding variables)

[rich]

Here's my code:
function doMath() {

var grandTot=0;
var one=new Array(13);
var two=new Array(13);
var prod=new Array(13);
one[1] = eval(document.form1.BFPpric.value);
two[1] = eval(document.form1.BFPquantity.value);
one[2] = eval(document.form1.BFTTpric.value);
two[2] = eval(document.form1.BFTTquantity.value);

etc down to 13 then

for (var i = 1; i < 14; i++) {
prod[i] = one[i] * two[i];
grandTot += prod[i];
}
}

There will always be some prod[i] in there that will be 0 (zero)
value, because not every item is ordered.
grandTot always totals to 0 (zero)!!!!! WHY??
It's making me nuts!!

[VK]

ri**@away32.com wrote:

Here's my code:
function doMath() {

var grandTot=0;
var one=new Array(13);
var two=new Array(13);
var prod=new Array(13);
one[1] = eval(document.form1.BFPpric.value);
two[1] = eval(document.form1.BFPquantity.value);
one[2] = eval(document.form1.BFTTpric.value);
two[2] = eval(document.form1.BFTTquantity.value);

etc down to 13 then

for (var i = 1; i < 14; i++) {
prod[i] = one[i] * two[i];
grandTot += prod[i];
}
}

There will always be some prod[i] in there that will be 0 (zero)
value, because not every item is ordered.
grandTot always totals to 0 (zero)!!!!! WHY??

Mostly because eval(string) has nothing to do with math. You maybe were
thinking of parseInt or parseFloat.

[bheku]

ri**@away32.com wrote:

Here's my code:
function doMath() {

var grandTot=0;
var one=new Array(13);
var two=new Array(13);
var prod=new Array(13);
one[1] = eval(document.form1.BFPpric.value);
two[1] = eval(document.form1.BFPquantity.value);
one[2] = eval(document.form1.BFTTpric.value);
two[2] = eval(document.form1.BFTTquantity.value);

etc down to 13 then

for (var i = 1; i < 14; i++) {
prod[i] = one[i] * two[i];
grandTot += prod[i];
}
}

There will always be some prod[i] in there that will be 0 (zero)
value, because not every item is ordered.
grandTot always totals to 0 (zero)!!!!! WHY??
It's making me nuts!!

I think VK explained pretty nicely, but I wanted to add a tip that may
save you going nuts in future.

Ideally, test just one line of code or portions of it. So for example
in your code, the thing to check before going further is:

eval(document.form1.BFPpric.value);

And if you kept getting 0 as an answer regardless of what value you put
in your form field, you would know that there maybe something wrong
with the way you're trying to retrieve the values.

This would probably have led you to the conclusion that eval() is not
giving you the answers you expect and you'd have searched the net for
its proper use or for an alternative way of extracting form field
values.

It may seem trivial to you at this point, but believe me, when your
scripting starts to get more and more complex, you'll appreciate this
kind of approach.

[mick white]

ri**@away32.com wrote:

Here's my code:
function doMath() {

>
var grandTot=0;
var one=new Array(13);
var two=new Array(13);
var prod=new Array(13);

var one=[],two=[],prod=[]

one[1] = eval(document.form1.BFPpric.value);
two[1] = eval(document.form1.BFPquantity.value);
one[2] = eval(document.form1.BFTTpric.value);
two[2] = eval(document.form1.BFTTquantity.value);

one[1] = +(document.form1.BFPpric.value);
// Attempt to cast value as a number

>
etc down to 13 then

var V=one.length;
for (var i = 1; i <= V; i++) //Number of products may change over time

for (var i = 1; i < 14; i++) {

if(!one[i] || !two[i] || isNaN(one[i]) || isNaN(two[i])) {continue}

//you need to do some checking of inputs, and remember multiplication by
zero results in zero

Mick

prod[i] = one[i] * two[i];
grandTot += prod[i];
}
}

There will always be some prod[i] in there that will be 0 (zero)
value, because not every item is ordered.
grandTot always totals to 0 (zero)!!!!! WHY??
It's making me nuts!!

[Richard Cornford]

bheku wrote:

ri**@away32.com wrote:

<snip>

>one[1] = eval(document.form1.BFPpric.value);
two[1] = eval(document.form1.BFPquantity.value);
one[2] = eval(document.form1.BFTTpric.value);
two[2] = eval(document.form1.BFTTquantity.value);

etc down to 13 then

for (var i = 1; i < 14; i++) {
prod[i] = one[i] * two[i];
grandTot += prod[i];
}
}

<snip>

>grandTot always totals to 0 (zero)!!!!! WHY??
It's making me nuts!!

I think VK explained pretty nicely,

That is unfortunate for you, as VK missed the mark by a long way and
instead fixated on an unrelated issue. While it is inadvisable to use
the - eval - method to convert numeric strings to numbers it is not
inadvisable because it doesn't work (rather it is inadvisable because
it is the least efficient method of doing so, and has completely
unpredictable results when the input is not string representations of
numbers), and its use will not explain why the total value of -
grandTot - is zero (and not NaN, which would be expected from most
circumstances when the input was not in the form of numeric strings).

Richard.