In this branch I implemented matches() which works like in XState: https://github.com/matthewp/robot/tree/matches

That is, you can do something like this:

service.matches('foo.bar');

Which will return true of the state is foo and the child machine's state is bar. This is pretty nice.

However, one thing I've wanted for a while is the ability to do unions for matching. In JavaScript you can use bitwise operators to do union matching, like so:

const Red = 1;
const Yellow = 1 << 1;
const Green = 1 << 2;

const CanGo = Yellow | Green;

It would be cool to incorporate this into Robot some how. What if you could pass such a union into a service.matches() API like so:

service.machine.current; // "yellow";

service.matches(Yellow); // true
service.matches(Green); // false
service.matches(CanGo); // true

I'd like to explore possibly allowing for such a thing. This would likely mean creating the state bits so users don't have to. Here's a possibly api:

const { yellow, green } = machine.states;

service.matches(yellow | green);

This seems fine. What about child states though? I would want to incorporate these some how as well so you can do the sort of service.matches('foo.bar') check that's shown at the top of this issue.