### countVowels

Retuns `number` of vowels in provided string.

Use a regular expression to count the number of vowels `(A, E, I, O, U)` in a `string`.

```js
const countVowels = str => (str.match(/[aeiou]/gi) || []).length;
```

```js
countVowels('foobar'); // 3
countVowels('gym'); // 0
```