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:

<scriptsrc='state-machine.js'></script>

after downloading the source or the minified version

Using npm:

 npm install --save-dev javascript-state-machine

In Node.js:

varStateMachine=require('javascript-state-machine');

Usage

A state machine can be constructed using:

varfsm=newStateMachine({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 state s is the current state
• 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 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.

You might also want to support this project by purchasing a commercial license.

Release Notes

See RELEASE NOTES file.

License

Dual-licensed under the LGPL for the open source community and also available with support under a commercial license.

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