Discussion on: Daily Challenge #219 - Compare Strings

function strCount(text, letter) {
  if (!letter.length) {
    return 'a letter is required.';
  }

  return text.split('').filter(i => i === letter).length;
}

console.log(strCount('Hello world', '')) // a letter is required.
console.log(strCount('Hello world', 'l')) // 3