Can anyone explain to me why
01/10/2003 is a number according to isNaN/parseFloat?
Example code:
<html>
<head>
<title> New Document </title>
</head>
<body>
<script>
function isNumber(str)
{
if (isNaN(parseFloat(str))) alert("not a number");
else alert("number");
}
</script>
<form name="f1" onSubmit="return false">
Text: <input type="text" name="t1"><br>
<input type="button" onClick="isNumber(this.form.t1.value)" value="is
number?">
</body>
</html>
--
--
~kaeli~
A man needs a mistress... just to break the monogamy. http://www.ipwebdesign.net/wildAtHeart http://www.ipwebdesign.net/kaelisSpace 6  1130 
kaeli said:
Can anyone explain to me why
01/10/2003 is a number according to isNaN/parseFloat?
<http://devedge.netscape.com/library/manuals/2000/javascript/1.5/reference/toplev.html#1064132>
parseFloat parses its argument, a string, and returns a floating point number.
If it encounters a character other than a sign (+ or -), numeral (0-9), a
decimal point, or an exponent, it returns the value up to that point and
ignores that character and all succeeding characters.
It only returns NaN if the first character cannot be converted to a number.
Hi,
kaeli wrote: Can anyone explain to me why
01/10/2003 is a number according to isNaN/parseFloat?
Example code:
<snipped>
If you alert the result of the parseFloat operation, you'll see that the
number is parsed until the parser finds the first character which
doesn't make sense. In this case, you'll get 1.
This behaviour is consistent in all browsers I know. I don't find this a
bad thing, as long as you know that it's so.
HTH,
Laurent
--
Laurent Bugnion, GalaSoft
Software engineering: http://www.galasoft-LB.ch
Private/Malaysia: http://mypage.bluewin.ch/lbugnion
Support children in Calcutta: http://www.calcutta-espoir.ch
In article <3f********@news.bluewin.ch>, ga*********@bluewin.ch
enlightened us with...
(thanks to both respondents) If you alert the result of the parseFloat operation, you'll see that the
number is parsed until the parser finds the first character which
doesn't make sense. In this case, you'll get 1.
This behaviour is consistent in all browsers I know. I don't find this a
bad thing, as long as you know that it's so.
Well, I think it's a bad thing, personally, because something like an
address (123 Blue Ave) would then verify as a number, which it is not.
Phone numbers would also be numbers, which they really aren't, since
adding them makes no sense.
But, since now I know, I can code around it.
Thanks!
--
--
~kaeli~
To steal ideas from one person is plagiarism; to steal from
many is research. http://www.ipwebdesign.net/wildAtHeart http://www.ipwebdesign.net/kaelisSpace
In article <MP************************@nntp.lucent.com>, kaeli
<ti******@NOSPAM.comcast.net> writes:
Well, I think it's a bad thing, personally, because something like an
address (123 Blue Ave) would then verify as a number, which it is not.
Phone numbers would also be numbers, which they really aren't, since
adding them makes no sense.
But, since now I know, I can code around it.
Thanks!
As written, your function will say that its a number. Its a flaw in the
function, not a flaw in the mechanisms. When you use parseFloat, it does just
that. It starts at the beginning and when it encounters a non-digit, it stops
and returns what it found. Basically what you are asking is "Does it start with
digits"?
function isNumber(str)
{
if (isNaN(parseFloat(str))) alert("not a number");
else alert("number");
}
Any string that starts with digits will pass, any that start with non-digits
(or nothing at all) will fail it.
function isNumber(str)
{
if (isNaN(+str)) alert("not a number");
else alert("number");
}
Using the unary + to attempt to convert it to number would come closer to what
you are describing though. As above, if it contains non-digits then it wont
convert it to a number.
<URL: http://msdn.microsoft.com/library/de...n-us/script56/
html/js56jsmthisfinite.asp />
isFinite(+str)
is an alternative to the function.
--
Randy
JRS: In article <3f********@news.bluewin.ch>, seen in
news:comp.lang.javascript, Laurent Bugnion, GalaSoft <galasoft- LB@bluewin.ch> posted at Tue, 6 Jan 2004 20:40:25 :- kaeli wrote:
Can anyone explain to me why
01/10/2003 is a number according to isNaN/parseFloat?
If you alert the result of the parseFloat operation, you'll see that the
number is parsed until the parser finds the first character which
doesn't make sense. In this case, you'll get 1.
This behaviour is consistent in all browsers I know. I don't find this a
bad thing, as long as you know that it's so.
It is a good thing; there is no more reason to recognise 01/10/2003 as a
date meaning 1st Oct 2003 than to recognise it as a division resulting
in 0.00004992511233150275. The interpretation of a string must depend
on the means chosen to interpret it.
--
© John Stockton, Surrey, UK. ?@merlyn.demon.co.uk Turnpike v4.00 MIME. ©
Web <URL:http://www.merlyn.demon.co.uk/> - FAQish topics, acronyms, & links.
Proper <= 4-line sig. separator as above, a line exactly "-- " (SonOfRFC1036)
Do not Mail News to me. Before a reply, quote with ">" or "> " (SonOfRFC1036)
kaeli <ti******@NOSPAM.comcast.net> writes:
[parseFloat only parsing inital part of string] Well, I think it's a bad thing, personally, because something like an
address (123 Blue Ave) would then verify as a number,
But parseFloat is not meant for verification. It is meant to parse the
inital part of a string to a number (probably intended for use in
parsing input, but not very useful for that, since it doesn't tell
how many characters it matched).
If you just want to convert the entire string to a number, use the
Number function. It gives NaN if the string is not a valid numeral.
The Number function works exactly the same as the internal type
conversion of Javascript.
/L
--
Lasse Reichstein Nielsen - lr*@hotpop.com
DHTML Death Colors: <URL:http://www.infimum.dk/HTML/rasterTriangleDOM.html>
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