In theory, maybe. In practice, your UI thread very rarely has to do the kind of heavy lifting that would block it so badly you actually have problems. I have e

In theory, maybe. In practice, your UI thread very rarely has to do the kind of heavy lifting that would block it so badly you actually have problems. I have encountered this -- for example parsing very large incoming JSON payloads -- but very rarely. And if you really need to mitigate it, there are webworkers.