Javascript validation for UTF-8 chatacters

[Madha K]

I am developing a web application that need to support UTF-8
characters.
For client side validations, can javascript be used to handle UTF-8
characters.
1) How javascript can be used to restrict non-utf8 characters?
2) Using javascript how to find the lengh of a string having unicode
characters?
e.g: For a field Name on the form, there is a corrosponding field Name
varchar2(10) in DB. Through my application when i try enter 10 normal
(i.e A-Z) characters, JDBC smoothly updates the DB.
But when my input has some 10 funny UTF8 characters, JDBC throws error
"inserted value too large".
Is there any javascript through which i can validate the input length
agaist the DB field size.

Thanks
Madha

[Stewart Gordon]

Re: Javascript validation for UTF-8 chatacters

Madha K wrote:[color=blue]
> I am developing a web application that need to support UTF-8
> characters.
> For client side validations, can javascript be used to handle UTF-8
> characters.[/color]
<snip>

You're in the wrong 'group.

http://smjg.port5.com/faqs/web/js/javaisnotjs.html

Stewart.

--
My e-mail is valid but not my primary mailbox. Please keep replies on
the 'group where everyone may benefit.

[Mahda]

Re: Javascript validation for UTF-8 chatacters

Hi Stewart,
I doubt if you have really gone through my question.
Please note that i dont want any help in java but want some javascript
help for client side validations.

Please let me know if you have any idea about such javascript.

Thanks



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[Martin Honnen]

Re: Javascript validation for UTF-8 chatacters



Madha K wrote:
[color=blue]
> I am developing a web application that need to support UTF-8
> characters.
> For client side validations, can javascript be used to handle UTF-8
> characters.[/color]

Script engines in Netscape 4.06 and later and IE 4 and later and other
modern browsers implementing the ECMAScript edition 3 standard can
handle Unicode characters, internally I think UTF-16 is used as the
encoding but in your HTML pages having the script the encoding doesn't
matter, if you have a JavaScript string you have an Unicode string where
each character has an Unicode character code.
[color=blue]
> 1) How javascript can be used to restrict non-utf8 characters?[/color]

The script doesn't know about the encoding, a string is simply a
sequence of Unicode characters.
[color=blue]
> 2) Using javascript how to find the lengh of a string having unicode
> characters?[/color]

string.length
[color=blue]
> e.g: For a field Name on the form, there is a corrosponding field Name
> varchar2(10) in DB. Through my application when i try enter 10 normal
> (i.e A-Z) characters, JDBC smoothly updates the DB.
> But when my input has some 10 funny UTF8 characters, JDBC throws error
> "inserted value too large".
> Is there any javascript through which i can validate the input length
> agaist the DB field size.[/color]

As said, a JavaScript string is a sequence of Unicode characters, how
that is stored on the server in a data base doesn't depend on how script
on the client represents the string.
And it doesn't make much sense to to client-side validation without
server-side validation implemented first as JavaScript can be disabled
or simply not being supported.



--

Martin Honnen

http://JavaScript.FAQTs.com/

[Michael Winter]

Re: Javascript validation for UTF-8 chatacters

On 07 Sep 2004 12:01:57 GMT, Mahda <Kmah@yahoo.com > wrote:
[color=blue]
> Hi Stewart,
> I doubt if you have really gone through my question.[/color]

He didn't really need to; you cross-posted a Javascript question to a Java
newsgroup. Stewart's post was merely pointing that out.
[color=blue]
> Please note that i dont want any help in java but want some javascript
> help for client side validations.[/color]

Going back to your original post, Javascript always handles Unicode
characters: strings are internally converted to Unicode sequences. The
best form of input validation usually involves regular expressions that
ensure the user follows some format. A length check is a simple comparison
of the length property:

var elems = document.forms['formName'].elements;
if(elems['elementName'].value.length < comparison here >) {
// do stuff
}

To validate a form when it's submitted, you would use something like:

<form ... onsubmit="retur n validate(this)" >

function validate(form) {
var elements = form.elements;

if(10 < elements['elementName'].value.length) {
alert('Please limit your value to 10 characters.');
elements['elementName'].focus();
return false;
}
// More validation
return true;
}

If the form field, elementName, had a value greater than 10 characters,
the user would be notified and the form would not be submitted. The
statement, return false, cancels the submission.

Don't forget that you can attempt to limit the length of user input using
the maxlength property. You should still check the value though, just to
be safe.

The final thing you might want to consider is whether your input data is
being read properly by the server. If single Unicode characters are being
broken up into multiple bytes for transmission, is the server using those
bytes, or is it reforming the original characters? Not having dealt with
Unicode input, I couldn't say whether this was a possibility or not.

All that said, and this is important, you should not be relying on
Javascript to validate your page. The server *must* validate input and
should an error be found, respond with a page describing an error and
allowing for its correction. Client-side validation should only be used to
speed up the validation process and reduce server traffic. From what you
describe in your original post, you don't seem to be doing this.

[snip]

Hope that helps,
Mike

--
Michael Winter
Replace ".invalid" with ".uk" to reply by e-mail.