Write a function named countVowels that takes a single string as input and returns the number of vowels present in the string. The vowels are 'a', 'e', 'i', 'o', and 'u', and they can be either uppercase or lowercase.
Answer inside countVowels js file in root directory.
Write a function named reverseString that takes a single string as input and returns a new string with the characters in reverse order.
Answer inside reverseString js file in root directory.
Write a function named filterEvenNumbers that takes an array of numbers as input and returns a new array containing only the even numbers.