JavaScript/String/CountVowels.js

/**
 * @function countVowels
 * @description Given a string of words or phrases, count the number of vowels.
 * @param {String} url - The input string
 * @return {Number} count
 * @example countVowels("ABCDE") => 2
 * @example countVowels("Hello") => 2
 */

const countVowels = (str) => {
  if (typeof str !== 'string') {
    throw new TypeError('Input should be a string')
  }
  const vowels = new Set(['a', 'e', 'i', 'o', 'u'])
  let count = 0
  for (let i = 0; i < str.length; i++) {
    const char = str[i].toLowerCase()
    if (vowels.has(char)) {
      count++
    }
  }
  return count
}

export { countVowels }