Not much. The point is that such heavy diffing can be avoided if loops and conditionals are enough and if you don't need random HTML changes.

Once you have loops, conditionals and recursion, don't you have "random HTML changes"?

Exactly. Loops and conditionals should give you enough power.

But in React you can arbitrarily change HTML because the render method returns a string to be compared to the earlier situation.

A tag name can change for example (which you rarely need).

> But in React you can arbitrarily change HTML because the render method returns a string to be compared to the earlier situation.

I'm pretty sure the render method returns a vdom node (which the library can then diff and merge into the actual DOM)

As a point of reference, virtual-dom is 17k when minified with the same settings and 5.8k when gzipped.

That's starting from the 42k 1.2.0 distfile.