State Machine implementations I've played with:

• XState – Statechart format – all bells and whistles – library – battle tested
• @xstate/fsm – 1KB full FSM – Flat format – library – battle tested
• Simple State Machine – Flat format – with named/inline actions, context, meta – home grown
• Micro State Machine – Flat format – with named actions – home grown
• Nano State Machine – Flat format – state tracking only – home grown