Javascript field validation

**Dr John Stockton** · Jul 23 '05, 04:48 PM

Re: Javascript field validation

JRS: In article <ee261922.05012 50153.5ce6146a@ posting.google. com>,
dated Tue, 25 Jan 2005 01:53:28, seen in news:comp.lang. javascript,
Colin Graham <csgraham74@hot mail.com> posted :
[color=blue]
> I have to write a validation check for two fields that they
>don't contain all the same characters e.g.,
>
>field 1 = 111111 field 2 = 11111111
>
>OR
>
>field 1 = 000000 field 2 = 00000000
>
>my script wants to check to see if this is happening and display an
>error message.[/color]

This checks a single field. Your question is unclear as to whether
field 1 = 11111 and field 2 = 22222 is good or bad. Checking the
concatenation of your fields does what you might want.

function Try(S) {
Bad = /^(.)(\1)+$/.test(S.value) // 1st character is followed by sames
if (Bad) { alert('Aaarrrgh !') ; S.focus() }
return !Bad }

Note - that accepts having only one character, which is necessarily all
the same; or none. Consider changing + to *.

OK = /(.)[^\1])/.test(S.value) // does not work, but
someone may be able to write a RegExp that tests only
for an instance of a character followed by a
different one.

See <URL:http://www.merlyn.demo n.co.uk/js-valid.htm>.

[color=blue]
>I would also be agreatful if anyone could point me towards any
>javascript code banks on the web as this would help speed up my
>learning.[/color]

In most cases, only if you consider them as probably bad examples - of
course, one can still learn something from them.

--
© John Stockton, Surrey, UK. ?@merlyn.demon. co.uk Turnpike v4.00 IE 4 ©
<URL:http://www.jibbering.c om/faq/> JL/RC: FAQ of news:comp.lang. javascript
<URL:http://www.merlyn.demo n.co.uk/js-index.htm> jscr maths, dates, sources.
<URL:http://www.merlyn.demo n.co.uk/> TP/BP/Delphi/jscr/&c, FAQ items, links.

rh · Jul 23 '05, 04:49 PM

Re: Javascript field validation

Dr John Stockton wrote:[color=blue]
> JRS: In article <ee261922.05012 50153.5ce6146a@ posting.google. com>,
> dated Tue, 25 Jan 2005 01:53:28, seen in news:comp.lang. javascript,[/color]

<...>
[color=blue]
>
>
> OK = /(.)[^\1])/.test(S.value) // does not work, but
> someone may be able to write a RegExp that tests only
> for an instance of a character followed by a
> different one.
>[/color]

Appears to have an extraneous ")", but I think you're right that a
backreference cannot be used there.

This perhaps?:

| OK = /^(.)(?!\1+$)/.test(S.value)
<...>

../rh

**RobB** · Jul 23 '05, 04:49 PM

Re: Javascript field validation

rh wrote:[color=blue]
> Dr John Stockton wrote:[color=green]
> > JRS: In article <ee261922.05012 50153.5ce6146a@ posting.google. com>,
> > dated Tue, 25 Jan 2005 01:53:28, seen in news:comp.lang. javascript,[/color]
>
> <...>
>[color=green]
> >
> >
> > OK = /(.)[^\1])/.test(S.value) // does not work,[/color][/color]
but[color=blue][color=green]
> > someone may be able to write a RegExp that tests[/color][/color]
only[color=blue][color=green]
> > for an instance of a character followed by a
> > different one.
> >[/color]
>
> Appears to have an extraneous ")", but I think you're right that a
> backreference cannot be used there.[/color]

Not in a negated character class, anyway.
[color=blue]
>
> This perhaps?:
>
> | OK = /^(.)(?!\1+$)/.test(S.value)[/color]

(snip)

Why would a zero-width assertion be needed?

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<title>untitled </title>
<script type="text/javascript">

function checkit()
{

var fchk = {
'val1' : 'value 1' ,
'val2' : 'value 2'
};

var f, ftop, msg = '';
for (fid in fchk)
{
f = document.getEle mentById(fid);
f.value = f.value.replace (/\s/g, '');
if (/^$/.test(f.value))
{
msg += fchk[fid] + ': blank\n';
ftop = ftop || f;
}
else if (/^(.)\1+$/.test(f.value))
{
msg += fchk[fid] + ': same characters\n';
ftop = ftop || f;
}
}
if (msg != '')
{
var bef = 'Errors noted:\n\n';
var aft = '\nPlease correct.\n';
alert(bef + msg + aft);
if (ftop && ftop.focus)
{
ftop.focus();
ftop.select();
}
return false;
}
return true;
}

</script>
</head>
<body>
<form onsubmit="retur n checkit()">
<input id="val1" type="text" name="val1" value="" />__value 1
<br />
<input id="val2" type="text" name="val2" value="" />__value 2
<hr />
<input type="submit" value="done" />
</form>
</body>
</html>

rh · Jul 23 '05, 04:49 PM

Re: Javascript field validation

RobB wrote:[color=blue]
> rh wrote:[color=green]
> > Dr John Stockton wrote:[color=darkred]
> > > JRS: In article[/color][/color][/color]
<ee261922.05012 50153.5ce6146a@ posting.google. com>,[color=blue][color=green][color=darkred]
> > > dated Tue, 25 Jan 2005 01:53:28, seen in[/color][/color][/color]
news:comp.lang. javascript,[color=blue][color=green]
> >
> > <...>
> >[color=darkred]
> > >
> > >
> > > OK = /(.)[^\1])/.test(S.value) // does not work,[/color][/color]
> but[color=green][color=darkred]
> > > someone may be able to write a RegExp that tests[/color][/color]
> only[color=green][color=darkred]
> > > for an instance of a character followed by a
> > > different one.
> > >[/color]
> >
> > Appears to have an extraneous ")", but I think you're right that a
> > backreference cannot be used there.[/color]
>
> Not in a negated character class, anyway.[/color]

Nor in a non-negated character class, if I recall the semantics
correctly.
[color=blue]
>[color=green]
> >
> > This perhaps?:
> >
> > | OK = /^(.)(?!\1+$)/.test(S.value)[/color]
>
> (snip)
>
> Why would a zero-width assertion be needed?
>[/color]

Uh, to make it work? ;-) (Note that it does not fully meet JRS's
suggestion of providing a test for differing adjacent characters.)
<..>

../rh

Javascript field validation

Javascript field validation

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