RegExp to validate an email address

[Andrew DeFaria]

I was reading my O'Reilly JavaScript The Definitive Guide when I came
across RegExp and thought I could tighten up my JavaScript code that
checks for a valid email address. Why does the following not appear to work:

var email_address = "Joe@Schmoe ";
var email_regex = new RegExp ("^(\\w+)(\@)(\ \w+)(\.)(\\w+)$ ");
var result = email_regex.exe c (email_address) ;
alert (" result[1] = \"" + result[1] + "\"\n" +
" result[2] = \"" + result[2] + "\"\n" +
" result[3] = \"" + result[3] + "\"\n" +
" result[4] = \"" + result[4] + "\"\n" +
" result[5] = \"" + result[5] + "\"");

The resulting alert box contains:

result[1] = "Joe"
result[2] = "@"
result[3] = "Schm"
result[4] = "o"
result[5] = "e"

It appears that the "\." is not escaping the "." to mean the literal
period. What am I doing wrong?
--
How come you don't ever hear about gruntled employees? And who has been
dissing them anyhow?

[Graham J]

Re: RegExp to validate an email address

> It appears that the "\." is not escaping the "." to mean the
literal[color=blue]
> period. What am I doing wrong?[/color]

You have "\." when you meant to put "\\." in the RegExp string.

[Thomas 'PointedEars' Lahn]

Re: RegExp to validate an email address

Andrew DeFaria wrote:
[color=blue]
> [...]
> var email_regex = new RegExp ("^(\\w+)(\@)(\ \w+)(\.)(\\w+)$ "
> [...]
> It appears that the "\." is not escaping the "." to mean the literal
> period. What am I doing wrong?[/color]

You did not notice consistently that the backslash is in string literals an
escape character, too. Therefore you need to escape it with another `\' if
you want a literal `\' to be passed to the RegExp constructor function, as
you did before and after. Otherwise it is ignored unless the combination
with the following character (here: `.') forms a known escape sequence, e.g.
`\n':

var email_regex = new RegExp ("^(\\w+)(@)(\\ w+)(\\.)(\\w+)$ "

But you can use RegExp literals instead which makes the Regular Expression
more legible since you need not to escape escape characters of strings:

var email_regex = /^(\w+)(@)(\w+)( \.)(\w+)$/;

BTW: In JavaScript, `@' need not to be escaped neither in string nor in
RegExp literals.


PointedEars

P.S.:
| Content-Type: multipart/alternative;
| boundary="------------020801000303080 605020808"

Please don't post Multipart HTML, Usenet is (except of
newsgroups where binaries are accepted) a text-only medium.
Uncheck Edit, Mail & Newsgroups Account Settings, $News_account,
Composition and Addressing, Compose messages in HTML format.
[color=blue]
> --[/color]

This preference setting will also make your signature separator
correct and working.

[Andrew DeFaria]

Re: RegExp to validate an email address

Thomas 'PointedEars' Lahn wrote:
[color=blue]
> Andrew DeFaria wrote:
>[color=green]
>> [...]
>> var email_regex = new RegExp ("^(\\w+)(\@)(\ \w+)(\.)(\\w+)$ "
>> [...]
>> It appears that the "\." is not escaping the "." to mean the literal
>> period. What am I doing wrong?[/color]
>
> You did not notice consistently that the backslash is in string
> literals a escape character, too. Therefore you need to escape it with
> another `\' if you want a literal `\' to be passed to the RegExp
> constructor function, as you did before and after. Otherwise it is
> ignored unless the combination
> with the following character (here: `.') forms a known escape
> sequence, e.g. `\n':
>
> var email_regex = new RegExp ("^(\\w+)(@)(\\ w+)(\\.)(\\w+)$ "[/color]

I had tried that. When I did the the following fails:

var email_address = "Joe@Schmoe ";
var email_regex = new RegExp ("^(\\w+)@(\\w+ )(\\.)(\\w+)$") ;
var result = email_regex.exe c (email_address) ;
alert ("Checking results");
alert (" result[0] = \"" + result[0] + "\"");
alert (" result[1] = \"" + result[1] + "\"");
alert (" result[2] = \"" + result[2] + "\"");
alert (" result[3] = \"" + result[3] + "\"");
alert (" result[4] = \"" + result[4] + "\"");

I get the "Checking results" alert but I do not get the result[0] alert.
As such I figured that the \\ in the \\. caused the problem.
[color=blue]
> But you can use RegExp literals instead which makes the Regular
> Expression more legible since you need not to escape escape characters
> of strings:
>
> var email_regex = /^(\w+)(@)(\w+)( \.)(\w+)$/;[/color]

You know I wanted to use that too but evertime I did my JavaScript just
blew up. Now it works! I think I forget the trailing ";" (I've been
writing a lot of Tcl at work where semicolons are not used at the end of
line).
[color=blue]
> BTW: In JavaScript, `@' need not to be escaped neither in string nor
> in RegExp literals.[/color]

I thought that but I was just backslashing it in case...

OK I think it got it working now. Thanks.
--
Lottery: A tax on people who are bad at math.

[Dr John Stockton]

Re: RegExp to validate an email address

JRS: In article <22e0d$3f9f6aa8 $44a7886c$23040 @msgid.meganews servers.co
m>, seen in news:comp.lang. javascript, Andrew DeFaria
<Andrew@DeFaria .com> posted at Tue, 28 Oct 2003 23:24:12 :-[color=blue]
>
> var email_address = "Joe@Schmoe ";
> var email_regex = new RegExp ("^(\\w+)(\@)(\ \w+)(\.)(\\w+)$ ");
> var result = email_regex.exe c (email_address) ;
> alert (" result[1] = \"" + result[1] + "\"\n" +
> " result[2] = \"" + result[2] + "\"\n" +
> " result[3] = \"" + result[3] + "\"\n" +
> " result[4] = \"" + result[4] + "\"\n" +
> " result[5] = \"" + result[5] + "\"");
>
>The resulting alert box contains:
>
> result[1] = "Joe"
> result[2] = "@"
> result[3] = "Schm"
> result[4] = "o"
> result[5] = "e"
>
>It appears that the "\." is not escaping the "." to mean the literal
>period. What am I doing wrong?[/color]

(1) posting in HTML/multi-part.

(2) having \ but not \\ before the dot.

ISTM better to express RegExps as literals -
RE = /^(\w+)(\@)(\w+) (\.)(\w+)$/

I see no need to escape the @,
nor to parenthesise the fixed parts @ and \. .

--
© John Stockton, Surrey, UK. ?@merlyn.demon. co.uk Turnpike v4.00 IE 4 ©
<URL:http://jibbering.com/faq/> Jim Ley's FAQ for news:comp.lang. javascript
<URL:http://www.merlyn.demo n.co.uk/js-index.htm> JS maths, dates, sources.
<URL:http://www.merlyn.demo n.co.uk/> TP/BP/Delphi/JS/&c., FAQ topics, links.

[Thomas 'PointedEars' Lahn]

Re: RegExp to validate an email address

Would you please configure your news client correctly as
I asked and described at the bottom of my previous posting?

Andrew DeFaria wrote:
[color=blue]
> Thomas 'PointedEars' Lahn wrote:[color=green]
>> var email_regex = new RegExp ("^(\\w+)(@)(\\ w+)(\\.)(\\w+)$ "[/color]
>
> I had tried that. When I did the the following fails:
>
> var email_address = "Joe@Schmoe ";
> var email_regex = new RegExp ("^(\\w+)@(\\w+ )(\\.)(\\w+)$") ;
> var result = email_regex.exe c (email_address) ;
> alert ("Checking results");[/color]
52:[color=blue]
> alert (" result[0] = \"" + result[0] + "\"");
> alert (" result[1] = \"" + result[1] + "\"");
> alert (" result[2] = \"" + result[2] + "\"");
> alert (" result[3] = \"" + result[3] + "\"");
> alert (" result[4] = \"" + result[4] + "\"");
>
> I get the "Checking results" alert but I do not get the result[0] alert.
> As such I figured that the \\ in the \\. caused the problem.[/color]

Yes, but different than you think. The above is the correct RegExp but it
only matches strings that contain a dot. The value of `email_address' here
("Joe@Schmoe ") simply does not contain a dot, so there is no match and
`result' therefore has no zero-property or no zeroth subexpression match
(which would be equal to the string the whole RegExp matches):

| Error: result has no properties
| Source File: http://localhost/scripts/test/test2
| Line: 52

In contrast, "\." in the string which resulted in the subexpression /./,
matches *any* character, namely the last `o' (since the second \w+ is
greedy and the last \w+ matches `e'), so result[0] is "Joe@Schmoe " and
not `undefined'.

Try

alert(new RegExp("^(\\w+) @(\\w+)(\\.)(\\ w+)$").exec("Jo e@Schmoe"));

and

alert(new RegExp("^(\\w+) @(\\w+)(\.)(\\w +)$").exec("Joe @Schmoe"));

to find this confirmed.
[color=blue][color=green]
>> var email_regex = /^(\w+)(@)(\w+)( \.)(\w+)$/;[/color]
>
> You know I wanted to use that too but evertime I did my JavaScript just
> blew up. Now it works! I think I forget the trailing ";" (I've been
> writing a lot of Tcl at work where semicolons are not used at the end of
> line).[/color]

The trailing `;' is optional (though recommended) unless you have
bad[tm] line-optimized code with two or more statements in a line.


HTH

PointedEars

[Andrew DeFaria]

Re: RegExp to validate an email address

Thomas 'PointedEars' Lahn wrote:
[color=blue]
> Would you please configure your news client correctly as I asked and
> described at the bottom of my previous posting?[/color]

Ah.... No.

--
I used to work at a factory where they made hydrants; but you couldn't
park anywhere near the place.

[Fabian]

Re: RegExp to validate an email address


"Thomas 'PointedEars' Lahn" <PointedEars@we b.de> wrote in message
news:3FA06928.5 010204@PointedE ars.de...[color=blue]
> Would you please configure your news client correctly as I asked and[/color]
described at the bottom of my previous posting?

Would you please reconfigure yours as I asked *you*? Your line lengths
are terrible!


--
--
Fabian
Visit my website often and for long periods!

http://www.lajzar.co.uk

[Thomas 'PointedEars' Lahn]

Re: RegExp to validate an email address

Fabian wrote:
[color=blue]
> "Thomas 'PointedEars' Lahn" <PointedEars@we b.de> wrote in message
> news:3FA06928.5 010204@PointedE ars.de...[color=green]
>> Would you please configure your news client correctly as I asked and[/color]
> described at the bottom of my previous posting?
>
> Would you please reconfigure yours as I asked *you*?[/color]

Message-ID, please!
[color=blue]
> Your line lengths are terrible![/color]

I don't know what's wrong with your news client (in fact I do know:
it's b0rken by default,) but mine is doing line-break automagically at
76 characters (except of URIs) as supposed, according to the standards:

,--------------<http://www.rfc-editor.org/rfc/rfc2822.txt>---------------
| 2.3. Body
|
| The body of a message is simply lines of US-ASCII characters. The
| only two limitations on the body are as follows:
|
| [...]
|
| - Lines of characters in the body MUST be limited to 998 characters,
| and SHOULD be limited to 78 characters, excluding the CRLF.

If you don't believe me, let Google Groups be the referee:

http://groups.google.com/groups?q=msgid%3A%3C3FA06928.5010204%40PointedEars.de%3E&ie=UTF-8&oe=UTF-8

HTH & HAND

PointedEars

[Lasse Reichstein Nielsen]

Re: RegExp to validate an email address

"Fabian" <lajzar@hotmail .com> writes:
[color=blue]
> "Thomas 'PointedEars' Lahn" <PointedEars@we b.de> wrote in message
> news:3FA06928.5 010204@PointedE ars.de...[color=green]
> > Would you please configure your news client correctly as I asked and[/color]
> described at the bottom of my previous posting?
>
> Would you please reconfigure yours as I asked *you*? Your line lengths
> are terrible![/color]

When I read the above two lines in the posting you reply to, none of
them is more than 72 characters. My newsreader doesn't wrap quotes
auotmatically, so I believe the problem is with your software.

In the message you replied to, there was only two lines (of
non-quotation) that were longer than 72 characters, and they were 73
and 74 respectively. Not something I would complain about.

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

[Dr John Stockton]

Re: RegExp to validate an email address

JRS: In article <wuanyprx.fsf@h otpop.com>, seen in
news:comp.lang. javascript, Lasse Reichstein Nielsen
<lrn@hotpop.com > posted at Thu, 30 Oct 2003 11:37:54 :-[color=blue]
>
>In the message you replied to, there was only two lines (of
>non-quotation) that were longer than 72 characters, and they were 73
>and 74 respectively. Not something I would complain about.[/color]

Agreed. Various RFCs and other sources suggest various margin
settings; for example FYI28 mentions 65 characters.

Given that there is a general expectation that most quoted lines
will not exceed 80 characters, and that some quoters use " >" as
indicator, ISTM that the right margin setting should not usually
exceed 72 characters for optimum results.

If the composing software permits quick altering of the margin
setting of a completed article, it may be worth trying a small
change when the text looks particularly ugly. I narrowed this
article a little, and the paragraphs are now almost justified.

--
© John Stockton, Surrey, UK. ?@merlyn.demon. co.uk Turnpike v4.00 IE 4 ©
<URL:http://jibbering.com/faq/> Jim Ley's FAQ for news:comp.lang. javascript
<URL:http://www.merlyn.demo n.co.uk/js-index.htm> JS maths, dates, sources.
<URL:http://www.merlyn.demo n.co.uk/> TP/BP/Delphi/JS/&c., FAQ topics, links.