title: Check if all values of array are of the same type
body: <p>Is there a good way to check if all items in an array are of the same type?</p>
  
  <p>Something that does this:</p>
  
  <pre><code>[1, 2, 3, 4]  // true
  [2, 3, 4, "foo"] // false
  </code></pre>