a problem with text field verification

gunawardana · Dec 23, 2003

I have to write a program to verify text field in HTML forms.
So,I hane to verify a text field with lenth 10 & maxlenth 10.The
entered text should be as follows.
xxxxxxxxxy
where xxxxxxxxx denotes a combination of numbers and y should be one
of 'X','x','V'or 'v'.Also inputs such as 000000000v,000000000X are not
possible.

lallous · Dec 23, 2003

Hello,

Validate the string as:

str="012345678x";
var pat = new RegExp(/[0-9]{9}[xv]/i);
if (pat.exec(str)==null)
alert('Invalid input!');

McKirahan · Dec 23, 2003

gunawardana said:
I have to write a program to verify text field in HTML forms.
So,I hane to verify a text field with lenth 10 & maxlenth 10.The
entered text should be as follows.
xxxxxxxxxy
where xxxxxxxxx denotes a combination of numbers and y should be one
of 'X','x','V'or 'v'.Also inputs such as 000000000v,000000000X are not
possible.

I'm sure there's a Regular expression that does what you want with less
coding but here's one solution; watch for word-wrap.

<html>
<head>
<title>gunawardana.htm</title>
<script language="javascript" type="text/javascript">

</script>
</head>
<body>
<form>
<input type="text" name="Data" size="10" maxlength="10">
<input type="button" value="Check" onclick="check()">
</form>
</body>
</html>

Dr John Stockton · Dec 23, 2003

JRS: In article <[email protected]>, seen

in news:comp.lang.javascript said:
I have to write a program to verify text field in HTML forms.
So,I hane to verify a text field with lenth 10 & maxlenth 10.The
entered text should be as follows.
xxxxxxxxxy
where xxxxxxxxx denotes a combination of numbers and y should be one
of 'X','x','V'or 'v'.Also inputs such as 000000000v,000000000X are not
possible.

But what do you mean by "such as"? With leading zero? With all zeroes?

There is an "or" facility in a RegExp, but not AFAIK an equivalent
"and".

Don't use a RegExp; use two, the second to deal with whatever "such as"
means.

OK = /^\d{9}(v|x)$/i.test(S) && /[1-9]/.test(S) // not 000000000
OK = /^\[1-9]d{8}(v|x)$/i.test(S) // not leading zero

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

Lasse Reichstein Nielsen · Dec 24, 2003

Dr John Stockton said:
There is an "or" facility in a RegExp, but not AFAIK an equivalent
"and".

Not directly. There could be, since there is nothing in the technology
used that prohibits and "and" (and regular languages are closed under
intersection).
The closest you get is positive lookahead, i.e., to match five digits
and at least one 4, you can write
/^(?=\d{5})\d*4\d*$/

Don't use a RegExp; use two,

Agreed. Often, a very complex regular expressin can be written as
two simple ones.

Example: String contains n "a"'s and m "b"'s:

Two regexps:
/^[^a]*(a[^a]*){n}$/
/^[^b]*(b[^b]*){m}$/

I won't even begin to write a regexp for n and m with values much over 2.
Try

/L

Eric Bohlman · Dec 24, 2003

Not directly. There could be, since there is nothing in the technology
used that prohibits and "and" (and regular languages are closed under
intersection).
The closest you get is positive lookahead, i.e., to match five digits
and at least one 4, you can write
/^(?=\d{5})\d*4\d*$/

Actually you can use positive lookahead to implement an arbitrary "and":
/^(?=.*this)(?=.*that)/ (a trick introduced in the _Perl Cookbook_ and
implemented in a Perl module of mine).

However, doing two separate tests will usually be more efficient and the
lookahead trick should probably be used only when the match parameters
aren't known until runtime.

Lasse Reichstein Nielsen · Dec 24, 2003

Eric Bohlman said:
Actually you can use positive lookahead to implement an arbitrary "and":
/^(?=.*this)(?=.*that)/ (a trick introduced in the _Perl Cookbook_ and
implemented in a Perl module of mine).

The problem is that you can only do this efficiently at the end of a string.
Compare this for "or':
/z(aa|bbb)cd/
If we had the hypothetical & operator, and wrote
/z(.*this.*&.*that.*)cd/
then we wanted the part between "z" and "cd" to contain both "this"
and "that".

If you do that with lookahead, you need to be able to bound the search
somehow, or the lookahead can test past the cd. As your example:
/z(?=.*this)(.*that.*)cd/
would incorrectly match
"z that cd this"

You need to ensure that the lookahead is only tested against the same
string as the other argument to "and".

You can do "the trick" and duplicate the continuation:
/z(?=.*this.*cd)(.*that.*cd)/
but even that can be broken by using more complex expressions. Take
"all digits, and at least three 4's":

/z(\d*&(.*4){3}.*)cd/
Doing the trick here gives
/z(?=\d*cd)(.*4){3}.*cd/
However, that also matches
"z111cd444cd"

Again, you have to build your RegExps so the lookahead is bounded,
something that was not necessary with the hypothetical "&" operator.

/L

Thomas 'PointedEars' Lahn · Dec 28, 2003

lallous said:
str="012345678x";
var pat = new RegExp(/[0-9]{9}[xv]/i);

No. Either

var pat = /\d{9}[xv]/i;

or

var pat = new RegExp("\\d{9}[xv]", "i");

if (pat.exec(str)==null)

if (! pat.test(str))

alert('Invalid input!');

[Top post]

Please do not do this, you are wasting
scarce and thus precious resources.

PointedEars

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a problem with text field verification

gunawardana

lallous

McKirahan

Dr John Stockton

Lasse Reichstein Nielsen

Eric Bohlman

Lasse Reichstein Nielsen

Thomas 'PointedEars' Lahn

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