If the sink always reads synchronously, this module should work fine,
however in some situations it will behave in correctly.

https://github.com/davidchase/pull-dom-events/blob/master/index.js#L7

If an event happens more than once before the sink has read again, it will call the callback twice.
(but with a new value)

There are different ways you could address this, depending on what behavior you want with dom events, but the simplest thing would be to unset callback before calling it.

if(callback) {
  let _cb = callback
  callback = null
  _cb(err, data)
}

then you know callback can never be called twice, even if it's called recursively (before itself has returned)

Another question is what do do about events that happen inbetween calls?
one idea would be to let them drop, so you could have a stream of mousemove events,
and whenever you call read you get either the most recent or the next mouse event.
If you just implement the above suggestion, you'll always get the next mouse event.

you could also keep the most recent event, and respond with that if it hasn't been read yet.

for keyboard events you might want to keep the sequence of events?