title: Can you filter characters (even duplicated) from an array?
body: <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-js lang-js prettyprint-override"><code>const stringConvert = string =&gt; {
    let splitString = string.split("");
    let vowels = splitString.filter(letters =&gt; {
      return letters === "a", "e", "i", "o", "u"
    })
    return console.log(vowels);
  };
  
  
  stringConvert("Why don't you try and split this string into vowels, please?");</code></pre>
  </div>
  </div>
  </p>
  <p>The code above comes back undefined and I am trying to create a function that takes a string and counts how many vowels are in it. So far I have used the .split() to create an array with each individual character of the string and then I tried using .filter() to filter out each character that is a vowel.</p>
  <p>What (only vanilla javascript) would allow me to filter out each vowel from an array, so then I could use .length on that array to get the number of vowels?</p>