How to check if character is a letter in Javascript?

Question

I am extracting a character in a Javascript string with:

var first = str.charAt(0);

and I would like to check whether it is a letter. Stran

Answer 1

With respect to those special characters not being taken into account by simpler checks such as /[a-zA-Z]/.test(c), it can be beneficial to leverage ECMAScript case transformation (toUpperCase). It will take into account non-ASCII Unicode character classes of some foreign alphabets.

function isLetter(c) {
  return c.toLowerCase() != c.toUpperCase();
}

NOTE: this solution will work only for most Latin, Greek, Armenian and Cyrillic scripts. It will NOT work for Chinese, Japanese, Arabic, Hebrew and most other scripts.