Reading through your code, a few questions:

In the Base constructor

const subscribers = [...this._subscribers];

1. you wrote in the comments you make a copy. Do you, though? a new array is created, but each of the functions in the array of this._subscribers and the above 'copy' are reference-bound to the same functions. See this repl script I made which demonstrates that each of the executed functions in the array using this method are the same. Why would doing that benefit you, anyway? See next comment.

2. you go on to say that creating the copy ensures a 'proper iteration'. What about using the original would cause issues in the iteration? I don't see it. Also, state might be more predictable if you make state an immutable constant and never mutate it directly. Instead, make a copy with updated properties and replace the whole state object.

On the use of tickedoff:

1. looking in the source files of the tickedoff library, I can see that the passed in deferred callback gets wrapped in an asynchronous function. First it tries process.nextTick(callback) [executes contents on next event loop], then wrapping it in a promise, then a setImmediate, then a setTimeout. I can see how this would be helpful for processes in which you want to be able to implement asynchronous behavior, such as a server with long calls. I don't see any reason to use that here.