Need to validate form fields

Check if email addresses are typed correctly

[WebmasterFisherman]

Hi

I need to check if email addresses in the form field are correct i.e. have @ and domain.com or subdomain.domain.com
syntax

Perhaps somebody here could help?

[DrDoc]

Validating e-mail addresses is a lot more complicated than it may sound. You need to make sure that the address follows general domain name standards, as well as make sure that there are no invalid characters, or valid characters in the wrong place :)

Normally I'm not a fan of doing anyone's homework, but I'll post this little snippet anyway. It's taken from a PHP script, but the same principle applies whether you use Perl/PHP/JavaScript/whatever. Just remember, if you use a client side solution (such as JavaScript) you should implement a server side solution as well. Anyway, here goes:

if(strlen($_POST['email'])<7 ¦¦
!preg_match("/^[-_.[:alnum:]]*[-_[:alnum:]]@((([[:alnum:]]¦
[[:alnum:]][[:alnum:]-]*[[:alnum:]])\.)*([[:alnum:]][[:alnum:]-]*
[[:alnum:]])\.(ad¦ae¦aero¦af¦ag¦ai¦al¦am¦an¦ao¦aq¦ar¦arpa¦as¦at¦
au¦aw¦az¦ba¦bb¦bd¦be¦bf¦bg¦bh¦bi¦biz¦bj¦bm¦bn¦bo¦br¦bs¦bt¦bv¦bw¦
by¦bz¦ca¦cc¦cd¦cf¦cg¦ch¦ci¦ck¦cl¦cm¦cn¦co¦com¦coop¦cr¦cs¦cu¦cv¦cx
¦cy¦cz¦de¦dj¦dk¦dm¦do¦dz¦ec¦edu¦ee¦eg¦eh¦er¦es¦et¦eu¦fi¦fj¦fk¦fm¦
fo¦fr¦ga¦gb¦gd¦ge¦gf¦gh¦gi¦gl¦gm¦gn¦gov¦gp¦gq¦gr¦gs¦gt¦gu¦gw¦gy¦
hk¦hm¦hn¦hr¦ht¦hu¦id¦ie¦il¦in¦info¦int¦io¦iq¦ir¦is¦it¦jm¦jo¦jp¦ke
¦kg¦kh¦ki¦km¦kn¦kp¦kr¦kw¦ky¦kz¦la¦lb¦lc¦li¦lk¦lr¦ls¦lt¦lu¦lv¦ly¦
ma¦mc¦md¦mg¦mh¦mil¦mk¦ml¦mm¦mn¦mo¦mp¦mq¦mr¦ms¦mt¦mu¦museum¦mv¦mw¦
mx¦my¦mz¦na¦name¦nc¦ne¦net¦nf¦ng¦ni¦nl¦no¦np¦nr¦nt¦nu¦nz¦om¦org¦
pa¦pe¦pf¦pg¦ph¦pk¦pl¦pm¦pn¦pr¦pro¦ps¦pt¦pw¦py¦qa¦re¦ro¦ru¦rw¦sa¦
sb¦sc¦sd¦se¦sg¦sh¦si¦sj¦sk¦sl¦sm¦sn¦so¦sr¦st¦su¦sv¦sy¦sz¦tc¦td¦tf
¦tg¦th¦tj¦tk¦tm¦tn¦to¦tp¦tr¦tt¦tv¦tw¦tz¦ua¦ug¦uk¦um¦us¦uy¦uz¦va¦
vc¦ve¦vg¦vi¦vn¦vu¦wf¦ws¦ye¦yt¦yu¦za¦zm¦zw)¦
(([0-9][0-9]?¦[0-1][0-9][0-9]¦[2][0-4][0-9]¦[2][5][0-5])\.){3}
([0-9][0-9]?¦[0-1][0-9][0-9]¦[2][0-4][0-9]¦[2][5][0-5]))$/i",
$_POST['email']) ¦¦ strpos($_POST['email'],".")===0) {
echo "* Please enter a valid e-mail address";
}

Note: The red lines must all be on one line!

[Purple Martin]

You can check for @ using

if (myString.indexOf("@") > 0) { 

etc

and build your own simple email checker using the same idea for . as well.

I did it myself once, luckily I've still got the code. This simple function checks that the e-mail address has an @ symbol, something before the @, and someting with a . in it after the @. It's not foolproof but it'll make sure people at least attempt to get their e-mail address right. The function accepts a string, and returns true or false.

function checkEmail(email) {
  var good = true
  var at = email.indexOf("@")
  var dot = email.lastIndexOf(".")
  if (email == "") { good = false }
  if (at < 1) { good = false }
  if (dot < at + 2) { good = false }
  if (dot > (email.length - 3)) { good = false }
  return good
}

There are better ones than this available, but it's small and simple and a lot better than nothing. And like DrDoc said, you have to check server-side as well, in case the user has JavaScript turned off!

[DrDoc]

Purple Martin,

Your validator will fail if I enter an address such as [e-mail], which is a perfectly valid address ;)

[Duncs]

DR DOC,

look on the bright side, if anyone wants to use you email validator and "take the easy option" rather than write their own they still have to change every one of these: ¦ manually back to the ones our text editors accept!

Now thats a tedious task if i ever saw one!

Duncs

[panoylis]

with regexp something like

/^[\w-][\w-\.]+@[\w-][\w-]+(\.[a-zA-Z]{2,4})+$/

sould do for the lot.

will say true for [e-mail] or [e-mail]
but will not say true to [e-mail]

a change to

/^[\w-][\w-\.]+@[\w-][\w-]+(\.[\w-]+)*(\.[a-zA-Z]{2,4})+$/

sould work for [e-mail] and [e-mail]

am I right?!

Panos

[DrDoc]

Except that it would not let [e-mail] through. It would also fail for [e-mail], and allow [e-mail]...

I guess it depends on the level of validation you need. On the client side, I wouldn't worry too much, but on the server side you should always use a more comprehensive function to validate the user submitted data.

[WebmasterFisherman]

Thanks everyone

I am really just a JS newbie so it's more a matter of learning rather than functional thing and certainly not homework:)))

I really don't do server side and just started html 4 months ago.

I'm much more into non-technical things like SEO but willing to be developer-independent:)

It is merely client-side really
I just need to give window.alert if email format is wrong or send them to a different page if it's right

What would you say to a variant like this (based on Purple Martin snippet):

function checkEmail(email) {
var at = email.indexOf("@")
var dot = email.lastIndexOf(".")
if (email == "") ¦¦ (at < 1) ¦¦ (dot < at + 2) ¦¦ (dot > (email.length - 3)) {
window.alert('Your email format is incorrect!')
}
else
{ window.navigate('http://www.somesite.com');
}}

Doesn't seem to work though...

[DrDoc]

Use
location.href="http://www.somesite.com";
instead of window.navigate

[Purple Martin]

Purple Martin,

Your validator will fail if I enter an address such as [e-mail], which is a perfectly valid address ;)

Oh no it won't!

Have another look DrDoc, that address works just fine. As far as I can tell there aren't any fatal flaws with my validator (if there are I'd love to hear about them).

;)

[DrDoc]

Opps... Had another look :(
And you're absolutely right, so, sorry 'bout that :)

However, it still will let foobar@.foo.com (or

me@.!@#$.com

for that matter) through ;)
But, that's a different story...
I'm just playing the devil's advocate

[TheDoctor]

window.alert('Your email format is incorrect!')

Don't use this sort of error message. Sooner or later you will release a piece of software that has a validation bug in it, and you will end up telling a user that the format of their email address is incorrect when they know full well that it isn't. They're liable to go away in anger.

Better is something like "I don't recognise your email address". This is more accurate, sounds less high-handed and, if it turns out that the routine does have a bug in it, gives you a chance of retreating gracefully, because it doesn't say who's right and who's wrong. It just points out a mismatch between what the user entered and what the routine expected.