svelte5-fsm

A tiny (0.8kB) but surprisingly flexible finite state machine that uses Svelte 5's $state rune for reactivity.

Installation

``bash
npm install svelte5-fsm
`

Alternatively, just copy the fsm.svelte.ts file to your project.

Svelte 5 is required. This library is not compatible with older versions.

Usage

`svelte


machine.send('INCREMENT')} class:disabled={machine.state === 'full'}>Increment
machine.send('DECREMENT')} class:disabled={machine.context.count === 0}>Decrement
machine.send('RESET')}>Reset



Current state: {machine.state}

Count: {machine.context.count}



`

API

$3

#### new FSM(context: Context, states: States, initial: string, config?: Config)
Creates a new finite state machine.

- context - The context object that will be passed to each state.
- states - The state configuration object.
- on - The event handlers for the state. Can be a string representing the next state, or a function that returns the next state. The context is passed as a parameter to the function.
- guard - The guard function that determines if the state can be entered. Can return a boolean or a string. If it returns a string, the state machine will transition to that state instead. The context is passed as a parameter to the function.
- enter - The function that is called when the state is entered. The context is passed as a parameter to the function.
- goto - State to transition to immediately after entering. Run after guard and enter.
- config - The configuration object for the state machine.
- initial - The initial state of the machine. Must be a key of the states object.
- debug - Whether to log state transitions to the console.

Look at the code for exact type signatures if you need them.

#### machine.send(event: string, data?: any, context?: Context)
Sends an event to the state machine, which will trigger a state transition. Additional data can be passed to the event handler. Changes to the context object can be made by passing a context object or by doing them inside the event handler.

- event - The event to send.
- data - The data to pass to the event handler.
- context - The context object to pass to the state.

#### machine.start(context?: Context)
Starts the state machine from the initial state with the optional context object.

#### machine.state
The current state of the machine (declared as a $state).

#### machine.context
The context object of the machine (declared as a $state).

Examples

Look at the src` folder for more examples.

License

MIT