I listened to an old lecture from Crockford on Javascript (2006) and he was talking about the model

```none
Flow  -> Paint
  ^        | 
  |        v
Script <- Event

```

(a loop involving Flow, paint, event, script ...), saying "because all browsers are single threaded".

So, my question is, are they still single threaded?

And for those who might know, are these video lectures still relevant in terms of what is taught?