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So, maybe i'm misunderstanding, but, the perf advantage is that react waits until the next RAF and then only updates the parts of the DOM that actually changed? So, now i'm wondering: why can't the browser do that? Isn't this whole middle-man approach something to eventually be optimized out?

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The browser does do this already to an extent.

The difference is that React constrains the operations a user can do (i.e. we only give them the DOM node if they explicitly ask for it and only let them manipulate it at certain times) so we eliminate the operations that cause the DOM to be slow.

If the DOM were to implement this it'd have to break backwards compatibility.

Sure, the browser could implement a virtual dom and then sync it and do a reflow once per frame.

You can do that with the help of `document.createDocumentFragment()`.

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