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AFSM

FSM class

FSM is the base class for all state machines, extending eventemitter3’s EventEmitter.

Generics

class FSM<
  EventTypes extends EventEmitter.ValidEventTypes = string | symbol,
  Context extends any = any
> extends EventEmitter<EventTypes | FSMEventTypes, Context>
  • EventTypes — custom event type declarations (for type-safe emit/on)
  • Context — EventEmitter context
interface MyEvents {
  play: [url: string]
  stateChanged: [State, State, any]
}
class Player extends FSM<MyEvents> { ... }

Instance properties

state: State

Current state (getter). State = string | MiddleState.

const obj = new MyFSM()
console.log(obj.state)   // '[*]'

The setter also triggers setState (dispatches events), but usually you should change state via @ChangeState.

_state: State

Internal state field (the backing store for state). Direct mutation does NOT dispatch events — use with caution.

stateDiagram: string[]

Read-only getter. Auto-generates mermaid stateDiagram-v2 lines from decorator metadata. Memoized on the prototype after first access.

name?: string

Instance name, used for DevTools display. Auto-generated on construction (based on timestamp or parent name + counter).

groupName?: string

Group name, defaults to constructor.name. Used to categorize in the DevTools tree.

Instance methods

Inherited from eventemitter3:

  • on(event, cb) — listen
  • once(event, cb) — one-time listen
  • off(event, cb) — remove
  • emit(event, ...args) — dispatch
  • removeAllListeners(event?) — remove all or specific event listeners

updateDevTools(payload?)

Sends an update to the DevTools extension. Usually called automatically by setState — no need to call manually. The library also keeps a last-known snapshot per instance and replays it when the extension dispatches __AFSM_DUMP__.

Constructor

constructor(name?: string, groupName?: string, prototype?: any)
  • name — optional instance name
  • groupName — optional group name
  • prototype — internal use (for FSM.get proxy instances)
class Player extends FSM {
  constructor() {
    super('player', 'media')   // name='player', groupName='media'
  }
}

Static constants

ConstantValue
FSM.STATECHANGED'stateChanged'
FSM.UPDATEAFSM'updateAFSM'
FSM.INIT'[*]'
FSM.ON'on'
FSM.OFF'off'

Static registries

FSM.instances: Map<string, IFSM>

String-keyed instance registry, used by the context composition pattern.

FSM.instances2: WeakMap<object, IFSM>

Object-keyed instance registry.

FSM.get(context: string | object): IFSM

Get or create the FSM associated with a context. If absent, creates a minimal proxy instance via Object.create(FSM.prototype) and registers it.

const fsm = FSM.get('shared-timer')
const same = FSM.get('shared-timer')
console.log(fsm === same)  // true

FSM.getState(context: string | object): State

Directly fetch a context’s state (returns undefined if absent).

Internal symbols

These symbols are for internal state — don’t access directly in normal use:

  • [cacheResult] — caches the last successful result
  • [abortCtrl] — abort control (reserved)

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