Javascript State Machine
A library for finite state machines.
NOTE for existing users
VERSION 3.0 Is a significant rewrite from earlier versions.
Existing 2.x users should be sure to read the Upgrade Guide.
Installation
In a browser:
<script src='state-machine.js'></script>
after downloading the source or the minified version
Using npm:
npm install --save-dev javascript-state-machine
In Node.js:
var StateMachine = require('javascript-state-machine');
Usage
A state machine can be constructed using:
var 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' }
],
methods: {
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.is(s)- return true if statesis the current statefsm.can(t)- return true if transitiontcan occur from the current statefsm.cannot(t)- return true if transitiontcannot occur from the current statefsm.transitions()- return list of transitions that are allowed from the current statefsm.allTransitions()- return list of all possible transitionsfsm.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 and Methods.
Multiple instances of a state machine can be created using a State Machine Factory.
Documentation
Read more about
- States and Transitions
- Data and Methods
- Lifecycle Events
- Asynchronous Transitions
- Initialization
- Error Handling
- State History
- Visualization
- State Machine Factory
- Upgrading from 2.x
Contributing
You can Contribute to this project with issues or pull requests.
Release Notes
See RELEASE NOTES file.
License
See MIT LICENSE file.
Contact
If you have any ideas, feedback, requests or bug reports, you can reach me at
jake@codeincomplete.com, or via
my website: Code inComplete