compare comes back wrong

I am comparing two numbers, and the comparison gives absolutely bizzare
results. I am comparing 5 with a number that is entered in a form. Then
if the number entered is 5, or between 50 and 95, it gives the correct
answer, but if it is 10 to 45, or over 99, it does not. What the heck
is it doing here?

Here is the code:

if (form.quantity.value < form.minimum.value) printerror = printerror +
"\nThere is a minimum quantity of " + form.minimum.value;

form.minimum.value is set to 5. form.quantity.value is set according to
what is entered in the form.

It appears to be doing a string comparison on the numbers, but all the
documentation I find says that it should be doing a numeric computation.

Marshall

re: compare comes back wrong

On Mar 1, 9:06 pm, Marshall Dudley <mdud...@king-cart.comwrote:A string compared with another string gives alphabetic comparison
results. What documentation does say opposite?

if (+form.quantity.value < +form.minimum.value) is the simplest way to
get numeric comparison.

re: compare comes back wrong

Marshall Dudley wrote:
if (+form.quantity.value < +form.minimum.value) printerror = printerror +You should check that the input is indeed a number:
if (isNaN(form.quantity.value)||
(+form.quantity.value < +form.minimum.value)){
printerror = printerror +
"\nThere is a minimum quantity of " + form.minimum.value;
}

Mick

re: compare comes back wrong

Marshall Dudley said:Throw away all the documentation you found. It's all wrong.
Form control values are *always* strings.


--

re: compare comes back wrong

On Mar 1, 10:06 am, Marshall Dudley <mdud...@king-cart.comwrote:Don't know what documentation you're looking at, but you need to
convert your strings to numbers before doing a comparision:

var qty = +form.quantity.value, min = +form.minimum.value;
// more verbose, but equivalent:
var qty = parseInt(form.quantity.value, 10), min =
parseInt(form.quantity.value, 10);

if (qty < min) printerror += '\nThere is a minimum quantity of ' +
min;

-David

re: compare comes back wrong

VK wrote:Who's comparing strings? I am comparing numeric values. 5 and 95 are
numbers.I will try taht and see if it works.

Thanks,

Marshall

re: compare comes back wrong

On Mar 1, 10:01 pm, Marshall Dudley <mdud...@king-cart.comwrote:You are comparing two form input field values. Any form input value
for JavaScript is a Unicode string unless you explicetly instructed it
to think something else.

In case like
if (myForm.inputField.value 5)
JavaScript will try to convert the left string argument into number

In case like
if (myForm.inputField1.value myForm.inputField2.value)
it has no reason to make any conversions. The greater-than sign is
used for both alphabetical and numerical comparisons, and if both
arguments are strings then the engine's AI doesn't go so far to study
strings' content for some educated guess.

In many languages - and for a reason - there are two set of operators
for numerical and alphabetical comparison like / gt, < / lt etc.
JavaScript is not one of them, so it needs your help if both arguments
are strings but you really want to compare them as numbers.

re: compare comes back wrong

On Mar 1, 7:28 pm, "VK" wrote:I love this place. Although I knew what was wrong
in what he was doing, and what the solution was
(to convert to numbers), I didn't realize you can
just put a + in front of it. So that's a direct
replacement for wrapping a string that represents
a number in parseInt( ) ? I'd love to go through
all my code and replace them with a + (carefully by
hand of course, I wouldn't do a global replace, it
would be far too dangerous).

btw, while I'm here, anyone know why every time I
put a trimmed quote in my posts, it never gets
collapsed with a - Show quoted text - link like
all y'alls do ?

re: compare comes back wrong

"VK" <schools_ring@yahoo.comwrote:
Building on your original suggestion, but recognising that you only have to
explicitly force one side of the comparison to a numeric value:

If you wanted numeric comparison operators you could always pretend that
they are spelled "<+", ">+", etc.
true

BTW, you were wrong to say "A string compared with another string gives
alphabetic comparison results". String comparison compares unicode
character codepoints. So as soon as you go beyond simple ascii strings they
no longer compare alphabetically:
true

re: compare comes back wrong

On Mar 2, 9:38 am, dd wrote:The group's FAQ says that is so, and goes into details.
No. The - parseInt - function parses a string as an integer, and
throws away any trailing part of a string that cannot be interpreted
as part of an integer. Thus a string representation of a number with a
decimal fractional part will be truncated at the decimal point (and
representations of numbers with exponents get very unhelpful
handling). The - parseFloat - function would be a nearer comparison,
but the unary plus operator actually acts to type-convert from string
to number using type-conversion rules, so the whole string is
considered and the handling of strings that are not representations of
numbers is different in some cases.
Where that change is appropriate the rustles would be 7-14 times
faster.
Questions about the behaviour of particular web Usenet interfaces/news
readers should be directed to those responsible (or at least openly
interested).

Richard.

re: compare comes back wrong

On Mar 2, 9:46 am, Duncan Booth wrote:
<snip>Where is the need to go beyond ascii?

"5" < "40"

- is already non-alphabetic, but the characters are all ascii.

Richard.

re: compare comes back wrong

In comp.lang.javascript message <45e71c39$0$28099$4c368faf@roadrunner.co
m>, Thu, 1 Mar 2007 13:32:24, Michael White <mick@mickweb.composted:Yes, but that is a weak check. In many cases, numbers such as
Infinity -3 4.5 1e88 are clearly inappropriate regardless of the
numeric value, and an order quantity of 2000e-3 need not be accepted.
Generally, one can choose between allowing any input and validating
elsewhere, allowing any input and letting the user take the
consequences, or using a RegExp to constrain the input pattern quite
strongly.

Temp = form.quantity.value
Fail = /\D/.test(Temp) // ...
Nmbr = +Temp

--
(c) John Stockton, Surrey, UK. ?@merlyn.demon.co.uk Turnpike v6.05 MIME.
Web <URL:http://www.merlyn.demon.co.uk/- FAQqish topics, acronyms & links;
Astro stuff via astron-1.htm, gravity0.htm ; quotings.htm, pascal.htm, etc.
No Encoding. Quotes before replies. Snip well. Write clearly. Don't Mail News.