content/test/data/accessibility/output.html

<form onsubmit="return false" oninput="o.value = (a.valueAsNumber || 0) + (b.valueAsNumber || 0)">
 <input name=a type=number step=any> +
 <input name=b type=number step=any> =
 <output name=o for="a b"></output>
</form>