Javascript field validation

Colin Graham · Jan 25, 2005

Hi there,

Im very new to javascript and this is my first bit of javascript
coding. 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.

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.

any help greatly appreciated.

Thanks

Colin

Dr John Stockton · Jan 25, 2005

JRS: In article <[email protected]>,
dated Tue, 25 Jan 2005 01:53:28, seen in

Colin Graham said:
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.

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.demon.co.uk/js-valid.htm>.

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.

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

rh · Jan 26, 2005

Dr said:
JRS: In article <[email protected]>,
dated Tue, 25 Jan 2005 01:53:28, seen in news:comp.lang.javascript,

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.

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 · Jan 26, 2005

rh said:
Dr said:

JRS: In article <[email protected]>,
dated Tue, 25 Jan 2005 01:53:28, seen in news:comp.lang.javascript,

Click to expand...

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.

Click to expand...

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

Not in a negated character class, anyway.

This perhaps?:

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

(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.getElementById(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="return 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 · Jan 26, 2005

RobB said:
rh said:

Dr said:

JRS: In article

Click to expand...

dated Tue, 25 Jan 2005 01:53:28, seen in

Click to expand...

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.

Click to expand...

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

Click to expand...

Not in a negated character class, anyway.

Nor in a non-negated character class, if I recall the semantics
correctly.

(snip)

Why would a zero-width assertion be needed?

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 Validate Form Fields	1	Jan 25, 2005
Very Basic CC Validation Javascript	0	Oct 29, 2019
javascript validation for a not required field, field is onlyrequired if another field has a value	3	Jul 8, 2010
Javascript validation question	2	Jul 31, 2007
javascript validation for mixed form	0	Apr 26, 2007
Complex Form Validation	5	Dec 31, 2005
Who are low code solutions designed for?	1	Oct 22, 2023
Python vs "Low Code" solutions for SaaS development	0	Oct 22, 2023

Javascript field validation

Colin Graham

Dr John Stockton

rh

RobB

rh

Ask a Question

Similar Threads

Members online

Forum statistics

Latest Threads