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https://github.com/hqarroum/fsm
:vertical_traffic_light: A tiny implementation of a finite state machine in Javascript.
https://github.com/hqarroum/fsm
finite-state-machine fsm state-machine
Last synced: 26 days ago
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:vertical_traffic_light: A tiny implementation of a finite state machine in Javascript.
- Host: GitHub
- URL: https://github.com/hqarroum/fsm
- Owner: HQarroum
- License: mit
- Created: 2015-06-24T18:54:51.000Z (over 9 years ago)
- Default Branch: master
- Last Pushed: 2023-01-08T17:10:19.000Z (almost 2 years ago)
- Last Synced: 2024-05-23T03:03:41.374Z (6 months ago)
- Topics: finite-state-machine, fsm, state-machine
- Language: JavaScript
- Homepage:
- Size: 281 KB
- Stars: 5
- Watchers: 3
- Forks: 0
- Open Issues: 1
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
README
## Fsm
[](https://app.travis-ci.com/HQarroum/Fsm)
[](https://www.codefactor.io/repository/github/hqarroum/fsm)
[](https://deepsource.io/gh/HQarroum/Fsm/?ref=repository-badge)
A tiny implementation of a finite state machine written in Javascript.
Current version: **2.0.0**
Lead Maintainer: [Halim Qarroum](mailto:[email protected])
## Install
```bash
npm install --save fsm.js
```
## Usage
### Import the FSM
`Fsm.js` is distributed as an ESM module that you can import in your implementation.
```javascript
import Fsm from 'fsm.js';
```
### Creating the FSM
To create an instance of the state machine you simply have to call its constructor :
```javascript
const fsm = new Fsm();
```
### Creating a state
A `state` is an instance of a `Fsm.State` object. It takes a reference to the state machine it is associated with as well as optional callbacks associated with the state lifecycle.
As you can see below, creating a state is pretty straightforward :
```javascript
const state = new Fsm.State({
/**
* An optional name for the state.
*/
name: 'initialization',
/**
* A reference to the used state machine.
*/
fsm: fsm,
/**
* An optional callback invoked when the state is
* entered.
*/
onEntry: () => {},
/**
* An optional callback invoked upon a received
* event.
*/
onEvent: (event) => {
// Do something with the received `event`.
},
/**
* An optional callback invoked when the state is
* exited.
*/
onExit: () => {}
});
```
### Starting the state machine
When a state machine is created, it is stopped by default. To start a state machine you need to give it a reference to the initial state in which it should be starting :
```javascript
fsm.start(state);
```
### Playing around with events
Usually, you will want states to react to received events by executing actions and transitioning between one another. This can be achieved through the `postEvent` and `transitionTo` primitives as shown in the example below.
```javascript
/**
* The `initialization` state of the system.
*/
const initialization = new Fsm.State({
fsm: fsm,
name: 'initialization',
onEntry: () => console.log('Initialization ...'),
onExit: () => console.log('Initialization completed'),
onEvent: (event) => {
if (event === 'init.done') {
this.transitionTo(initialized);
}
}
});
/**
* The `initialized` state.
*/
const initialized = new Fsm.State({
fsm: fsm,
name: 'initialized',
onEntry: () => console.log('System initialized')
});
// Starting the fsm.
fsm.start(initializing);
// Simulating an asynchronous event.
setTimeout(() => fsm.postEvent('init.done'), 1000);
```
The above code will output :
```bash
Initialization ...
Initialization completed
System initialized
```
## Example
In the [elevator example](https://github.com/HQarroum/Fsm/blob/master/examples/elevator/index.js), we implemented, as an example of a real life problem, the bare minimum functions provided by an elevator using a finite state machine.
For the sake of simplicity, the implementation is really dummy, meaning that smart behaviours such as ordering of the levels given their location along the elevator path are not implemented.