<p dir="auto"><a href="http://facebook.github.io/react/docs/interactivity-and-dynamic-uis.html" rel="nofollow">http://facebook.github.io/react/docs/interactivity-and-dynamic-uis.html</a></p>
<p dir="auto">At the end, there is a confusing explanation about "Duplicated data from props" in the section "What Shouldn’t Go in State?":</p>
<blockquote>
<p dir="auto"><strong>Duplicated data from props:</strong> Try to use props as the source of truth where possible. Because props can change over time, it's appropriate to store props in state to be able to know its previous values.</p>
</blockquote>
<p dir="auto">Perhaps what is trying to be said is something like:</p>
<blockquote>
<p dir="auto"><strong>Duplicated data from props:</strong> Try to use props as the source of truth where possible. One valid use to store props in state is to be able to know it's previous values, because props can change over time.</p>
</blockquote>
<p dir="auto">Currently custom html attributes that start with 'x-' are not allowed.</p>
<p dir="auto">Here's a test case: <a href="http://jsbin.com/jehefo/edit?html,js,console" rel="nofollow">http://jsbin.com/jehefo/edit?html,js,console</a></p>
<p dir="auto">Allowing custom attributes would be helpful as for example things like Firefox OS use <code class="notranslate">x-inputmode="digit"</code> to provide a hint that the keyboard should only contain only digits. [1]</p>
<p dir="auto">[1] <a href="http://www.wufoo.com/html5/attributes/23-inputmode.html" rel="nofollow">http://www.wufoo.com/html5/attributes/23-inputmode.html</a></p>