In the past, React used to ignore unknown DOM attributes. If you wrote JSX with an attribute that React doesn't recognize, React would just skip it. For example, this:
would render an empty div to the DOM with React 15:
In React 16, we are making a change. Now, any unknown attributes will end up in the DOM:
Why Are We Changing This?
camelCase convention just like the DOM APIs:
This has not changed. However, the way we enforced it in the past forced us to maintain a whitelist of all valid React DOM attributes in the bundle:
... read the whole story at facebook.github.io.