Javascript function that restricts numeric functions but allow alphanumeric values

Question

i am stuck in a problem...This is my code which restricts special characters but i want a logic which will restricts special characters,numerics but allow alphanumeric values... for eg:

valid : a1,4r,aa.
invalid : w@,12,@!.

function check(e)

{

var keynum;
var keychar;
var numcheck;
if(window.event) // IE
{
    keynum = event.keyCode;
}
else if(e.which) // netscape/Firefox/opera
{
    keynum = e.which;
}

//condition for backspace(8) Key
if(keynum != 8)
{
    keychar = String.fromCharCode(keynum);
    numcheck = /[a-zA-Z0-9]*[a-zA-Z]+[a-zA-Z0-9]*/;
    return numcheck.test(keychar);
}
else
{
    return true;
}

}

    User id : <input type="text" id="txtname" name="txtname" onkeypress="return check(event)"/>

A simple [regular expression](http://www.javascriptkit.com/javatutors/re.shtml) should be enough. — Some programmer dude, Jan 31 '13 at 09:06
"Alphanumeric" means alphabetic + numeric characters, as explained in the [wiki](http://en.m.wikipedia.org/wiki/Alphanumeric). As such, what do you mean by "restrict numerics", but "allow alphanumerics"? — HartleySan, Jan 31 '13 at 09:06
Hartley... i want a1,4r,aa to be allowed but should not allow w@,12,@!. — , Jan 31 '13 at 09:07
So digits are okay _if_ they are together with letters, but not a "word" containing only digits? — Some programmer dude, Jan 31 '13 at 09:12
Similar question is already answered at http://stackoverflow.com/questions/388996/regex-for-javascript-to-allow-only-alphanumeric hope this helps ... — Abi, Jan 31 '13 at 09:12

score 0 · Answer 1 · edited May 23 '17 at 10:31

0

Alpha numeric validation from SO itself :

var reg_password1 = 'tes123';
var letters = /^[a-zA-Z0-9]+$/;

var result = letters.test(reg_password1);

alert(result);

See this question

Fiddle not by me

edited May 23 '17 at 10:31

Community

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answered Jan 31 '13 at 09:06

Nishant Jani

1,965
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it allows numeric only inputs also – Naveed S Jan 31 '13 at 09:39

Naveed S · Answer 2 · 2013-01-31T10:35:25.593

0

I think this is the regex you need :

^[A-Za-z0-9]*[A-Za-z]+[A-Za-z0-9]*$

It matches zero or more alphanumeric characters followed by atleast one letter followed by zero or more alphanumeric characters.

So it allows aa and 0r

and does not allow 99 or sequence containing non-alphanumeric characters.

Your question says only alphanumeric characters are allowed. Your example says aa. should be allowed. If so, use :

^[A-Za-z0-9.]*[A-Za-z]+[A-Za-z0-9.]*$

It allows . along with at least one letter such as .aa and aa.

Check it like this :

numcheck.test(inputString);

where inputString is the input like a23, we and .aa which are matched or 12 and k@ which are not matched

numcheck is /[A-Za-z0-9.]*[A-Za-z]+[A-Za-z0-9.]*/

edited Jan 31 '13 at 10:35

answered Jan 31 '13 at 09:12

Naveed S

5,106
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am sorry, i wanted to update my answer but by mistake edited your answer, and do not know how to undo edit. – Ali Shah Ahmed Jan 31 '13 at 09:17
sorry but its not working...its not allowing me to enter thye numbers...eg.a1.. – Jan 31 '13 at 09:22
@chetanPotdar check well. It allows `a1` – Naveed S Jan 31 '13 at 09:24
@chetanPotdar do you want to allow special characters along with letters? – Naveed S Jan 31 '13 at 09:26
No naveed it is not allowing me...i have edited my whole code...plz have a luk on it.. – Jan 31 '13 at 09:29
i dont want special chars – Jan 31 '13 at 09:30
@chetanPotdar check the new regex. If you want to allow `.` also, use that. – Naveed S Jan 31 '13 at 09:32
@chetanPotdar if it worked pls accept the answer. Otherwise pls make your requirement clear. – Naveed S Jan 31 '13 at 09:40
why my code is not working??? – Jan 31 '13 at 10:22
@chetanPotdar Are you checking each character in the input separately? Check the whole string against the regex. – Naveed S Jan 31 '13 at 10:26
i m nt getting u naveed...cn u correct the mistakes in my code plz – Jan 31 '13 at 10:33
how to chk the whole string??? – Jan 31 '13 at 10:39

score 0 · Accepted Answer · answered Jan 31 '13 at 09:14

I believe this would satisfy your need.

[a-zA-Z0-9]*[a-zA-Z]+[a-zA-Z0-9]*

This would restrict only numbers such as 12, 13, etc., would now allow any special character, and as required, would allow words containing alphabets and numbers both such as asd12, 12asd12, 12asd, etc.

Javascript function that restricts numeric functions but allow alphanumeric values

3 Answers3