# Help: Invalid character check

**URL:** <https://forum.kirupa.com/t/help-invalid-character-check/254878>\
**Category:** Uncategorized\
**Created:** [March 16, 2008, 8:30pm UTC](https://forum.kirupa.com/t/help-invalid-character-check/254878 "2008-03-16T20:30:33Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![Utech22](https://avatars.discourse-cdn.com/v4/letter/u/f17d59/32.png) [@Utech22](https://forum.kirupa.com/u/Utech22)\
**Post date:** [March 16, 2008, 8:30pm UTC](https://forum.kirupa.com/t/help-invalid-character-check/254878/1 "2008-03-16T20:30:33Z")

</div>

What is wrong with :

```auto

function check ( char )
{
var valid = ( [^a-zA-Z 0-9] );
if (char.code.value == "" || char.code.value != valid ) 
{
    alert( "Please enter a code ." );
    char.code.focus();
    return false ;
}
  return true ;
}

```