t;, [/* ... */]) // uppercase
// I know these look odd, but `brick-deck`&#39;s `selectedIndex` property is a
// string, not a number.
m(&quot;brick-deck&quot;, {&quot;selected-index&quot;: &quot;0&quot;}, [/* ... */])
m(&quot;brick-deck&quot;, {&quot;selectedIndex&quot;: &quot;0&quot;}, [/* ... */])</code></pre>
<p>For custom elements, it doesn&#39;t auto-stringify properties, in case they are objects, numbers, or some other non-string value. So assuming you had some custom element <code>my-special-element<