title: How do I type a array that has a mix of number and object (named array)
body: <p>I have this sample code:</p>
  <pre><code>const arr = [320, 480, 1024];
  arr.small = arr[0];
  arr.medium = arr[1];
  arr.large = arr[2];
  </code></pre>
  <p><code>console.log(arr)</code> will output:</p>
  <pre><code>[320, 480, 1024, small: 320, medium: 480, large: 1024]
  </code></pre>
  <p>What would be the type (interface on typescript) of <code>arr</code>?</p>
  <p>note: It might seem weird, but it's common on a design system theme file, where you want support by scale or by naming.</p>