Typescript State Machine

A strongly typed library for finite state machines.

Installation

npm install fsm-typescript --save-dev

Usage

A state machine can be constructed using:

const fsm = new StateMachine({
  init: 'solid',
  transitions: [
    { name: 'melt', from: 'solid', to: 'liquid' },
    { name: 'freeze', from: 'liquid', to: 'solid' },
    { name: 'vaporize', from: 'liquid', to: 'gas' },
    { name: 'condense', from: 'gas', to: 'liquid' },
  ],
  lifecycles: {
    onMelt: function () {
      console.log('I melted')
    },
    onFreeze: function () {
      console.log('I froze')
    },
    onVaporize: function () {
      console.log('I vaporized')
    },
    onCondense: function () {
      console.log('I condensed')
    },
  },
})

... which creates an object with a current state property:

fsm.state

... methods to transition to a different state:

fsm.melt()
fsm.freeze()
fsm.vaporize()
fsm.condense()

... observer methods called automatically during the lifecycle of a transition:

onMelt()
onFreeze()
onVaporize()
onCondense()

... along with the following helper methods:

fsm.can(t) - return true if transition t can occur from the current state
fsm.cannot(t) - return true if transition t cannot occur from the current state
fsm.transitions() - return list of transitions that are allowed from the current state
fsm.allTransitions() - return list of all possible transitions
fsm.allStates() - return list of all possible states

Terminology

A state machine consists of a set of States

solid
liquid
gas

A state machine changes state by using Transitions

melt
freeze
vaporize
condense

A state machine can perform actions during a transition by observing Lifecycle Events

onBeforeMelt
onAfterMelt
onLeaveSolid
onEnterLiquid
...

A state machine can also have arbitrary Data.

Documentation

License