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Answer 1

A:

You could matchall on regex which contains all the prohibited symbols (like your alphaExp), and then concatenate the matches.

EFraim 2009-07-20 11:28:30

Answer 2

+2 A:

Here's a simple way to do it... it's not be the most efficient though:

function isAlphabet(obj)
{
    var val = obj.value;
    var alphaExp = /[^a-z0-9_-]+/;

    var valid = true;
    var badchars = "";

    for( a = 0; a < val.length; a++ )
    {
     if(val[a].match(alphaExp))
     {
      badchars += "," + val[a];
      valid = false;
     }
    }

    if( !valid )
    {
     alert("The following characters are not allowed: " + badchars.substr(1));
     obj.focus();
    }

    return valid;
}

Kane Wallmann 2009-07-20 11:34:11

That doesn't work in Internet Explorer earlier than version 8. You have to use val.charAt(a) or val.substr(a,1) instead of val[a].

Guffa 2009-07-20 13:26:26

Answer 3

+1 A:

In this case, you are matching characters that do not fall into the supplied ranges. Therefore, you can put the matched text into a backreference and use that.

Alternatively, you can construct a Regexp object and use it's lastMatch property.

Cerebrus 2009-07-20 11:38:24

Answer 4

A:

if you use the g modifier, you can get .match() to return you an array of matches (invalid chars in your case) then you can just display them.

see "String.match(pattern)" about 1/3 down this page: http://evolt.org/regexp_in_javascript

var str = "Watch out for the rock!".match(/r?or?/g)

str then contains ["o","or","ro"]

Andrew Bullock 2009-07-20 11:39:14

Answer 5

+2 A:

Use a regular expression which matches the allowed characters to get a string where those are removed. If the string contains anything, the validation fails:

function isAlphabet(obj) {
   var alphaExp = /[a-z0-9_-]+/g;
   var illegal = obj.value.replace(alphaExp, '');
   if (illegal.length){
      alert('Input contains the characters '+illegal+' which are not allowed.');
      obj.focus();
      return false;
   } else {
      return true;
   }
}

Guffa 2009-07-20 11:47:10

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