check if char is alphabetic javascript code example

Example 1: checking if a character is an alphabet in js

function isLetter(str) {
  return str.length === 1 && str.match(/[a-z]/i);
}

Example 2: check for alphabetic string in javascript

function isAlphaOrParen(str) {
  return /^[a-zA-Z()]+$/.test(str);
}