Test for digit, regular expression

[Dave Miller]

Hello -

I have a form field the results from which should not start with a
digit. I have tried various permutations of the following without
success. Can anyone help me out?

//does not return false when it should
(document.my_fo rm.my_field.val ue.substring(0) == / \d /)

TIA

Dave Miller

[Evertjan.]

Re: Test for digit, regular expression

Dave Miller wrote on 17 okt 2003 in comp.lang.javas cript:
[color=blue]
> I have a form field the results from which should not start with a
> digit. I have tried various permutations of the following without
> success. Can anyone help me out?
>
> //does not return false when it should
> (document.my_fo rm.my_field.val ue.substring(0) == / \d /)[/color]

It should NOT. Please read up on Reg Ex.

=============== ========

If (/\d/.test(document. my_form.my_fiel d.value.substri ng(0)))

This will be true if the string contains at least 1 digit.

=============== =========

btw:

document.my_for m.my_field.valu e.substring(0)

and

document.my_for m.my_field.valu e

are equivalent

=============== =========

Not tested.

--
Evertjan.
The Netherlands.
(Please change the x'es to dots in my emailaddress)

[Ivo]

Re: Test for digit, regular expression

"Dave Miller" <unknown@unknow n.com> wrote in message
news:MPG.19fa01 7126c8c3959896a 7@news.pa.comca st.giganews.com ...[color=blue]
> Hello -
>
> I have a form field the results from which should not start with a
> digit. I have tried various permutations of the following without
> success. Can anyone help me out?
>
> //does not return false when it should
> (document.my_fo rm.my_field.val ue.substring(0) == / \d /)
>
> TIA
>
> Dave Miller[/color]

Remove the spaces from the regex, so
/ \d /
becomes
/\d/
That may give some very different results. Additionally,
/^\d/
will match any string that starts with a digit.

substring(0) returns the whole string, so you might as well use
document.my_for m.my_field.valu e
instead of
document.my_for m.my_field.valu e.substring(0)

You probably meant charAt(0), which is the first and nothing but the first
character, but using the ^ inside the regex should do the trick anyways in
this case.
Ivo

[Dave Miller]

Re: Test for digit, regular expression

In article <MPG.19fa017126 c8c3959896a7@ne ws.pa.comcast.g iganews.com>,
unknown@unknown .com says...


Thank you both for your help.

[TrueBlue]

Re: Test for digit, regular expression

why not using just a regular expression?
Sort of:

/^\d+/.test(document. formName.fieldN ame.value);

if it returns true, it means there are lweading digits. That's the most
practical way, uses the built in method test() which requires a reg expr as
its leading object. The regexp in case flags the following:
^ start of line
\d a digit
+ one or plus times

http://www.unitedscripters.com/

"Dave Miller" <unknown@unknow n.com>[color=blue]
>
> I have a form field the results from which should not start with a
> digit. I have tried various permutations of the following without
> success. Can anyone help me out?
>
> //does not return false when it should
> (document.my_fo rm.my_field.val ue.substring(0) == / \d /)[/color]

[Dr John Stockton]

Re: Test for digit, regular expression

JRS: In article <MPG.19fa017126 c8c3959896a7@ne ws.pa.comcast.g iganews.co
m>, seen in news:comp.lang. javascript, Dave Miller <unknown@unknow n.com>
posted at Fri, 17 Oct 2003 14:39:52 :-[color=blue]
>
>I have a form field the results from which should not start with a
>digit. I have tried various permutations of the following without
>success. Can anyone help me out?
>
>//does not return false when it should
>(document.my_f orm.my_field.va lue.substring(0 ) == / \d /)[/color]


The field.value is a string. There are exactly three types of string :
Starting with a digit
Starting with a non-digit
Not starting - i.e. = "" // do not forget this case

To test string S :
OK = !/^\d/.test(S) // does not start with digit
OK = /^\D/.test(S) // starts with non-digit

It seems likely that in practice you have other conditions on the entry;
the first-character test should be combined with the others using a
longer RegExp, e.g.

OK = /^\D.{3,5}$/.test(S) // non-digit; length 4..6

--
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