checking email address for @ and . characters

**Bart Van der Donck** · Jun 24 '06, 12:15 PM

Re: checking email address for @ and . characters

libsfan01 wrote:
[color=blue]
> Can anyone show me how to check and email field on a form for the
> existence of these two characters.[/color]

<html>
<head>
<meta http-equiv="Content-Type"
content="text/html; charset=iso-8859-1">
<script type="text/javascript">
// validates the format somechars@other chars.yetotherchars
function cM() {
/.+@.+\..+/.test(document. mF.email.value) ?
alert('OK') : alert('not OK');
}
</script>
</head>
<body>
<form name="mF" action="script. php">
<input type="text" name="email">
<input type="button" value="Check!" onClick="cM()">
</form>
</body>
</html>

(thanks Dr John Stockton,
http://www.merlyn.demon.co.uk/js-valid.htm#VEmA)

--
Bart

**Rik** · Jun 24 '06, 12:35 PM

Re: checking email address for @ and . characters

Bart Van der Donck wrote:[color=blue]
> function cM() {
> /.+@.+\..+/.test(document. mF.email.value) ?
> alert('OK') : alert('not OK');
> }[/color]

Or
/^[0-9a-z+_\.\-]+@([0-9a-z+_\.\-]+\.)+[a-z]{2,4}$/i

Allthough I'm not sure which characters are actually allowed in an
emailadress.

With the above code .@...%0dBcc:spa m@example.net;m ore@example.net seems a
totally valid emailadress..
Then again, I don't know where the validation is for, it could be
sufficient.

Grtz,
--
Rik Wasmus

**Noggon** · Jun 24 '06, 01:15 PM

Re: checking email address for @ and . characters

Rik wrote:[color=blue]
> Bart Van der Donck wrote:[color=green]
> > function cM() {
> > /.+@.+\..+/.test(document. mF.email.value) ?
> > alert('OK') : alert('not OK');
> > }[/color]
>
>
> Or
> /^[0-9a-z+_\.\-]+@([0-9a-z+_\.\-]+\.)+[a-z]{2,4}$/i[/color]

It is possible to have a one chracter domain name now or soon will be,
and a 5 character domain name too.

eg: .travel

**Rik** · Jun 24 '06, 01:45 PM

Re: checking email address for @ and . characters

Noggon wrote:[color=blue]
> Rik wrote:[color=green]
>> Bart Van der Donck wrote:[color=darkred]
>>> function cM() {
>>> /.+@.+\..+/.test(document. mF.email.value) ?
>>> alert('OK') : alert('not OK');
>>> }[/color]
>>
>>
>> Or
>> /^[0-9a-z+_\.\-]+@([0-9a-z+_\.\-]+\.)+[a-z]{2,4}$/i[/color]
>
> It is possible to have a one chracter domain name now or soon will be,
> and a 5 character domain name too.[/color]

check,
/^[0-9a-z+_\.\-]+@([0-9a-z+_\.\-]+\.)+[a-z]{1,6}$/i

Now, who can shed some light on allowed characters in emailadresses?

Grtz,
--
Rik Wasmus

**Bart Van der Donck** · Jun 24 '06, 03:15 PM

Re: checking email address for @ and . characters

Rik wrote:
[color=blue]
> [...]
> check,
> /^[0-9a-z+_\.\-]+@([0-9a-z+_\.\-]+\.)+[a-z]{1,6}$/i
>
> Now, who can shed some light on allowed characters in emailadresses?[/color]

Email address - Wikipedia

http://en.wikipedia.org/wiki/Email_address#Limitations

--
Bart

**Lasse Reichstein Nielsen** · Jun 24 '06, 03:15 PM

Re: checking email address for @ and . characters

"Rik" <luiheidsgoeroe @hotmail.com> writes:
[color=blue]
> /^[0-9a-z+_\.\-]+@([0-9a-z+_\.\-]+\.)+[a-z]{2,4}$/i
>
> Allthough I'm not sure which characters are actually allowed in an
> emailadress.[/color]

That's reason enough *not* to be too specific. A prefectly good looking
email like me@example.com will probably be wrong, whereas
me+bad@[192.168.10.2] might be correct (for another IP address at least).
[color=blue]
> Then again, I don't know where the validation is for, it could be
> sufficient.[/color]

You can't validate an email adress perfectly just by looking at it
(i.e., check that it is an email address that will receive mail
for the correct person). The only one who knows that is the person
writing it. It's *really* annoying to have a correct email address
rejected by an overzealous validator, so it's better to err on the
side of caution. For that, I prefer just checking for "@" and "."
in that order, which will at least catch really bad errors.

As for the specification, mail addresses were specified in RFC 822,
and probably revised in RFC 2822. Here is someone who has tried
interpreting it: <URL:http://www.cs.tut.fi/~jkorpela/rfc/822addr.html>

/L
--
Lasse Reichstein Nielsen - lrn@hotpop.com
DHTML Death Colors: <URL:http://www.infimum.dk/HTML/rasterTriangleD OM.html>
'Faith without judgement merely degrades the spirit divine.'

**Rik** · Jun 24 '06, 03:35 PM

Re: checking email address for @ and . characters

Bart Van der Donck wrote:[color=blue]
> Rik wrote:
>[color=green]
>> [...]
>> check,
>> /^[0-9a-z+_\.\-]+@([0-9a-z+_\.\-]+\.)+[a-z]{1,6}$/i
>>
>> Now, who can shed some light on allowed characters in emailadresses?[/color]
>
> http://en.wikipedia.org/wiki/Email_address#Limitations[/color]

Hmmz, is someone can elaborate on the _exact_ meaning of 'any hyphen of the
ascii character set'. Maybe it's the language difference, but if I translate
hyphen the only one i know is '-'....

So,
/^[0-9a-z!#$%&'*+\-\/=?^_`{|}~]+(\.*[0-9a-z!#$%&'*+\-\/=?^_`{|}~]+)*@([0-9a-
z\-]+\.)+[a-z]{1,6}$/i

Then again, let's not go as far as Friedl's tester, quoted emailadresses are
possible, a terrible, terrible thing to adjust for within limited code...

Grtz,
--
Rik Wasmus

**Rik** · Jun 24 '06, 03:35 PM

Re: checking email address for @ and . characters

Lasse Reichstein Nielsen wrote:[color=blue]
> "Rik" <luiheidsgoeroe @hotmail.com> writes:
>[color=green]
>> /^[0-9a-z+_\.\-]+@([0-9a-z+_\.\-]+\.)+[a-z]{2,4}$/i
>>
>> Allthough I'm not sure which characters are actually allowed in an
>> emailadress.[/color]
>
> That's reason enough *not* to be too specific. A prefectly good
> looking email like me@example.com will probably be wrong, whereas
> me+bad@[192.168.10.2] might be correct (for another IP address at
> least).
>[color=green]
>> Then again, I don't know where the validation is for, it could be
>> sufficient.[/color]
>
> You can't validate an email adress perfectly just by looking at it
> (i.e., check that it is an email address that will receive mail
> for the correct person). The only one who knows that is the person
> writing it. It's *really* annoying to have a correct email address
> rejected by an overzealous validator, so it's better to err on the
> side of caution. For that, I prefer just checking for "@" and "."
> in that order, which will at least catch really bad errors.[/color]

Well, then I'd at least do this:
/^[^\.@]+(\.*[^\.@]+)*@[^\.@](\.*[^\.@]+)+$/

Checking for the disallowes starting/ending dots is relativly simple to
incorporate.
It all depends on where you are going to use the emailadress for I suppose.

Grtz,
--
Rik Wasmus

**Bart Van der Donck** · Jun 24 '06, 06:15 PM

Re: checking email address for @ and . characters

Rik wrote:
[color=blue]
> [...]
>
> Well, then I'd at least do this:
> /^[^\.@]+(\.*[^\.@]+)*@[^\.@](\.*[^\.@]+)+$/
>
> Checking for the disallowes starting/ending dots is relativly simple to
> incorporate.
> It all depends on where you are going to use the emailadress for I suppose.[/color]

There's much more to it. If you're planning to write a solid email
address validator, I think you should at least scope it down to the RFC
you wish to comply with. Nowadays it looks as if RFC2822 would be a
good choice.

Javascript and Perl regular expression syntaces are quite similar,
maybe the following could be a start:

Client Challenge

http://search.cpan.org/~cwest/Email-Address-1.80/lib/Email/Address.pm

(=for RFC2822)

--
Bart

**libsfan01** · Jun 24 '06, 07:05 PM

Re: checking email address for @ and . characters

Sorry but i didnt get much from the solution, im looking for the JS
equivalent of php's function: strstr ( $haystack, $needle ) which
returns false if the needle is not found in the haystack.

is there something i can use which looks like this:

if (strstr( form.email.valu e, '@') == FALSE) { return false }

Bart Van der Donck wrote:[color=blue]
> Rik wrote:
>[color=green]
> > [...]
> >
> > Well, then I'd at least do this:
> > /^[^\.@]+(\.*[^\.@]+)*@[^\.@](\.*[^\.@]+)+$/
> >
> > Checking for the disallowes starting/ending dots is relativly simple to
> > incorporate.
> > It all depends on where you are going to use the emailadress for I suppose.[/color]
>
> There's much more to it. If you're planning to write a solid email
> address validator, I think you should at least scope it down to the RFC
> you wish to comply with. Nowadays it looks as if RFC2822 would be a
> good choice.
>
> Javascript and Perl regular expression syntaces are quite similar,
> maybe the following could be a start:
>
> http://search.cpan.org/~cwest/Email-...ail/Address.pm
> (=for RFC2822)
>
> --
> Bart[/color]

**libsfan01** · Jun 24 '06, 07:15 PM

Re: checking email address for @ and . characters

am i right in thinking indexof() is the baby for this

libsfan01 wrote:[color=blue]
> Sorry but i didnt get much from the solution, im looking for the JS
> equivalent of php's function: strstr ( $haystack, $needle ) which
> returns false if the needle is not found in the haystack.
>
> is there something i can use which looks like this:
>
> if (strstr( form.email.valu e, '@') == FALSE) { return false }
>
>
> Bart Van der Donck wrote:[color=green]
> > Rik wrote:
> >[color=darkred]
> > > [...]
> > >
> > > Well, then I'd at least do this:
> > > /^[^\.@]+(\.*[^\.@]+)*@[^\.@](\.*[^\.@]+)+$/
> > >
> > > Checking for the disallowes starting/ending dots is relativly simple to
> > > incorporate.
> > > It all depends on where you are going to use the emailadress for I suppose.[/color]
> >
> > There's much more to it. If you're planning to write a solid email
> > address validator, I think you should at least scope it down to the RFC
> > you wish to comply with. Nowadays it looks as if RFC2822 would be a
> > good choice.
> >
> > Javascript and Perl regular expression syntaces are quite similar,
> > maybe the following could be a start:
> >
> > http://search.cpan.org/~cwest/Email-...ail/Address.pm
> > (=for RFC2822)
> >
> > --
> > Bart[/color][/color]

**Randy Webb** · Jun 24 '06, 08:15 PM

Re: checking email address for @ and . characters

libsfan01 said the following on 6/24/2006 3:20 PM:[color=blue]
> am i right in thinking indexof() is the baby for this[/color]

"baby for this"? Are you writing JS or delivering babies?

indexof will tell you if a character is in a string but it is a long way
from doing what you original asked about.

@.yourHouse

indexOf('@') ==> true
indexOf('.') ==> true

@.yourMama ==> Nowhere close to an email address.
--
Randy
comp.lang.javas cript FAQ - http://jibbering.com/faq & newsgroup weekly
Temporarily at: http://members.aol.com/_ht_a/hikksnotathome/cljfaq/
Javascript Best Practices - http://www.JavascriptToolbox.com/bestpractices/

**John W. Kennedy** · Jun 24 '06, 09:45 PM

Re: checking email address for @ and . characters

Lasse Reichstein Nielsen wrote:[color=blue]
> You can't validate an email adress perfectly just by looking at it
> (i.e., check that it is an email address that will receive mail
> for the correct person). The only one who knows that is the person
> writing it. It's *really* annoying to have a correct email address
> rejected by an overzealous validator, so it's better to err on the
> side of caution. For that, I prefer just checking for "@" and "."
> in that order, which will at least catch really bad errors.[/color]

Even that will yield false positives in the trivial cases of mail
between two users on the same Unix system ("john") or two systems in the
same domain ("jane@payro ll" -- the ability to abbreviate
"payroll.wo rld-wide-wickets.com" to "payroll" in this way is the
historic reason that domains go right-to-left in the first place.)

--
John W. Kennedy
"The blind rulers of Logres
Nourished the land on a fallacy of rational virtue."
-- Charles Williams. "Taliessin through Logres: Prelude"

**Rik** · Jun 24 '06, 11:15 PM

Re: checking email address for @ and . characters

Bart Van der Donck wrote:[color=blue]
> Javascript and Perl regular expression syntaces are quite similar,
> maybe the following could be a start:
>
> http://search.cpan.org/~cwest/Email-...ail/Address.pm
> (=for RFC2822)[/color]

I'm actually more at home in PERL/PHP then javascript :-).
I'd have to look at tha package itself, maybe tomorrow. Then again, I saw
Friedl's solution for complete compliace with every possible valid
emailadress, and was in awe. I'm instantly giving up trying to get anywhere
near his solution. The damned thing is, when I try to find it again, I only
get references to his book, and my browser history has been cleaned in the
mean while....

Then again, maybe his book is a good purchase, really mastering regular
expressions is usually a time-saver in the first place, and rewriting them
when the reuirements change much simpler then huge quantaties of custom
code.

Grtz,
--
Rik Wasmus

checking email address for @ and . characters

checking email address for @ and . characters

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