An expressive, feature-rich, event-driven JavaScript finite-state machine
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JavaScript State Machine



State Machine is a library for managing a finite set of states, and moving between them via actions and transitions.

From its intuitive configuration through its powerful event-based architecture and rich API, State Machine makes it easy to describe and manage interaction with complex state-dependent systems like components, multi-step forms, purchase funnels, visualisations or games.


State Machine has been designed from the outset to feel intuitive and fun to use:

  • Easily-configurable via JavaScript config or instance methods
  • DSL for shorthand transition and handler assignment
  • Add and remove states and actions on the fly
  • Pause, resume, cancel or end transitions at any point
  • Handle system, state, action and transition events
  • Rich API and system introspection
  • Object-oriented architecture, fully-inspectable in DevTools


View the live demo at:

To run / tinker with the demo locally, see the Development section.


State Machine can be used directly in the browser, or in a Browserify, Node or ES6 project.

Install via NPM using:

npm install state-machine

Note: If you are expecting the package wheeyls/stateMachine it has now been depreciated. To continue to use that package in your project, ensure you use the version 0.3.0 in your package.json.


View the documentation at:



Clone the repo using:

git clone


The following NPM tasks are available, via npm run <task>:

  • dev - compile and watch the source to state-machine.js
  • build - compile the source to state-machine.min.js
  • demo - compile, watch and copy the development build to demo/ and serve demo files at http://localhost:8888
  • test - run all tests


To run a single or set of tests, use the following syntax:

  • npm run test -- --grep="<filename>"


Inspired by @jakesgordon's JavaScript State Machine.

Special thanks to Michael Wheeler (@wheeyls) who very kindly donated the NPM package name state-machine.