Don't forget about names like:

• Mathias d'Arras
• Martin Luther King, Jr.
• Hector Sausage-Hausen

This should do the trick for most things:

/^[a-z ,.'-]+$/i

OR Support international names with super sweet unicode:

/^[a-zA-ZàáâäãåąčćęèéêëėįìíîïłńòóôöõøùúûüųūÿýżźñçčšžæÀÁÂÄÃÅĄĆČĖĘÈÉÊËÌÍÎÏĮŁŃÒÓÔÖÕØÙÚÛÜŲŪŸÝŻŹÑßÇŒÆČŠŽ∂ð ,.'-]+$/u

What about:

• Peter Müller
• François Hollande
• Patrick O'Brian
• Silvana Koch-Mehrin

Validating names is a difficult issue, because valid names are not only consisting of the letters A-Z.

At least you should use the Unicode property for letters and add more special characters. A first approach could be e.g.:

String regx = "^[\\p{L} .'-]+$";

\\p{L} is a Unicode Character Property that matches any kind of letter from any language/script. \\p{L} is equivalent to \\p{javaLetter}, and both are equivalent to Character::isLetter.

function validate(id) {
    var regex = /^[a-zA-Z ]{2,30}$/;
    var ctrl =  document.getElemetnById(id);
    return regex.test(ctrl.value);
}

Yes! Let's validate some names with RegEx.

After all, we know that all people must have a first and last name, right? And no single person has more than three or four names total? And no doubt the same person will forever be identifiable by the same name?

Plus, we know that no modern culture uses patronymic naming and people in the same nuclear family must have the same last name, right?

Well, we can at least assume that people do not have single character names, right? And there are no names that use special characters, symbols, or apostrophes?

I think your choice of RegEx to validate names is missing the point: this is a huge unwieldy problem and, even if you massively restrict the scope of names you allow, you will forever suffer the risk of false negatives and you will be turning away people from other cultures and languages. In other words, I don't think that even attempting to validate names is worth your time.

Regex Returns TRUE if Text matches the regular expression RegEx_Text. Therefore if you Field is right then it gets true as result.

For Validation rules - If this formula expression is true, display the text defined in the Error Message area.

It's fine behavior then (at least it works as described in docs)

You can use

^A-Z[A-Za-z]*(?:\h+[A-Z][A-Za-z]*)*$

The pattern matches:

• ^ Start of string
• [A-Z] Match an uppercase char A-Z
• (?=.{1,29}$) Assert 1-29 chars to the right till the end of the string
• [A-Za-z]* Optionally match a char A-Za-z
• (?:\h+[A-Z][A-Za-z]*)* Optionally repeat 1+ horizontal whitespace chars followed by again an uppercase char A-Z and optional chars A-Za-z
• $ End of string

Regex demo

In Java with the doubled backslashes

String regex = "^A-Z[A-Za-z]*(?:\\h+[A-Z][A-Za-z]*)*$";

In this case, your code isn't working 'cause your regex was set as a string in the line:

 var reg="/^[a-zA-Z]*$/";

The regex was suposed to be set without quotes:

 var reg=/^[a-zA-Z]*$/;

I suggest that instead of the method 'match', you use:

else if (!reg.test(x)){

This is more performatic and return a boolean value.

You may use any of these 2 variants:

/^[A-Z]+$/i
/^[A-Za-z]+$/

to match an input string of ASCII alphabets.

• [A-Za-z] will match all the alphabets (both lowercase and uppercase).
• ^ and $ will make sure that nothing but these alphabets will be matched.

Code:

preg_match('/^[A-Z]+$/i', "abcAbc^Xyz", $m);
var_dump($m);

Output:

array(0) {
}

Test case is for OP's comment that he wants to match only if there are 1 or more alphabets present in the input. As you can see in the test case that matches failed because there was ^ in the input string abcAbc^Xyz.

Note: Please note that the above answer only matches ASCII alphabets and doesn't match Unicode characters. If you want to match Unicode letters then use:

/^\p{L}+$/u

Here, \p{L} matches any kind of letter from any language