typedfsm

A TypeScript Finite State Machine library.

Example

First create an enum with the states and possible actions on those states. It can have text values:

const enum GhostStates {
  Waiting = 'Waiting',
  Chasing = 'Chasing',
  Scatter = 'Scatter',
  Frightened = 'Frightened',
  Eaten = 'Eaten',
  Paused = 'Paused',
}

const enum GhostActions {
  Wait = 'Wait',
  Chase = 'Chase',
  Scatter = 'Scatter',
  Frighten = 'Frighten',
  Eat = 'Eat',
  Pause = 'Pause',
}

or just a plain numeric enum:

const enum GhostStates {
  Waiting,
  Chasing,
  Scatter,
  Frightened,
  Eaten,
  Paused,
}

const enum GhostActions {
  Wait,
  Chase,
  Scatter,
  Frighten,
  Eat,
  Pause,
}

To create the typed finite state machine use the following code with the previously defined enum and the start/default state of the machine as a parameter.

const ghostState = new Typed.FSM<GhostStates>(GhostStates.Waiting);

To create states/transitions we first call the from() method on the ghostState object, this will create a state of Waiting. To add a transition rule to this state we can chain the to() method to this call and give it the state Chasing. This will allow us to go from Waiting to Chasing but not from Chasing to Waiting. Next we call the toFrom() method which will create a transition rule to allow us to change from Waiting to Paused and from Paused back to Waiting.

ghostState
  .from(GhostStates.Waiting, GhostActions.Wait)
    .to(GhostStates.Chasing, GhostActions.Chase)
    .to(GhostStates.Scatter, GhostActions.Scatter)
    .toFrom(GhostStates.Paused, GhostActions.Pause);

To change the state of the finite state machine we can either specify the new state to change to:

ghostState.change(GhostStates.Chasing);

Or tell it an action to perform:

ghostState.do(GhostActions.Chase);