Simple verification

I wanted to make simple textarea verification in Javascript.

I wanted to prevent user from typing some characters, allowing only a..zA..Z0..9 '

I thought that when I return false during onKeyPress event associated with the textarea, it will prevent that character from displaying. But it doesn't work.

What's wrong?


Code:

function Onlyalfanum(key) {
c = false;
if (key>=97 && key<=122) c = true;
if (key>=65 && key<=90) c = true;
if (key>=48 && key<=57) c = true;
if (key==32 || key==39) c = true;
return c;
}

...
<textarea onKeyPress="return Onlyalfanum(event.keyCode)"></textarea>

You never use the variable the function returns. I suggest that in the form handler php script you do a regexp check.

Hmm, I have read somewhere (Javascript Reference Book I think), it should work this way. But the implementation have been changed, apparently.
I will look for up-to-date version.

To tkarkkainen: I want to do it on client-side so as not to waste server resources.