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@steelbreeze/state

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Readme

state

Executable finite state machine for TypeScript and JavaScript.

Notes:

v7 is now live and contains breaking changes but offers a much simplified code base and considerable performance improvements. See the release notes for more information.

@steelbreeze/state the new home for state.js and the versioning starts here from v6.0.0.

If you like @steelbreeze/state, please star it...

Install

npm i @steelbreeze/state

Usage

The API is broken up into two distinct parts:

A set of classes that represent a state machine model (State, PseudoState, Region, etc.);
An interface (IInstance), and default implementation of that interface (Instance), to represent an instance of a state machine model. This embodies the active state configuration of a state machine instance, and enables multiple instances of the same state machine model.

The full API reference can be found here.

TypeScript

import * as state from "@steelbreeze/state";

// log state entry, exit and trigger event evaluation
state.log.add(message => console.info(message), state.log.Entry | state.log.Exit | state.log.Evaluate);

// create the state machine model
const model = new state.State("model");
const initial = new state.PseudoState("initial", model, state.PseudoStateKind.Initial);
const stateA = new state.State("stateA", model);
const stateB = new state.State("stateB", model);

initial.to(stateA);
stateA.to(stateB).when(trigger => trigger === "move");

// create an instance of the state machine model
let instance = new state.Instance("instance", model);

// send the machine instance a message for evaluation
instance.evaluate("move");

// show the active state configuration as a JSON string
console.info(JSON.stringify(instance.toJSON()));

JavaScript

var state = require("@steelbreeze/state");

// log state entry, exit and trigger event evaluation
state.log.add(message => console.info(message), state.log.Entry | state.log.Exit | state.log.Evaluate);

// create the state machine model
var model = new state.State("model");
var initial = new state.PseudoState("initial", model, state.PseudoStateKind.Initial);
var stateA = new state.State("stateA", model);
var stateB = new state.State("stateB", model);

initial.to(stateA);
stateA.to(stateB).when(trigger => trigger === "move");

// create an instance of the state machine model
var instance = new state.Instance("instance", model);

// send the machine instance a message for evaluation
instance.evaluate("move");

// show the active state configuration as a JSON string
console.info(JSON.stringify(instance.toJSON()));

Output

The output of the above code will be:

instance enter model
instance enter model.model
instance enter model.model.initial
instance leave model.model.initial
instance enter model.model.stateA
instance evaluate string trigger: move
instance leave model.model.stateA
instance enter model.model.stateB
{"name":"model","children":[{"name":"model","children":[{"name":"stateA","children":[]},{"name":"stateB","children":[]}],"lastKnownState":"stateB"}]}

Note that in the example above, a default region is inserted as a child of model and parent of initial, stateA and stateB; the name of default regions copy their parent state hence seeing model.model in the output above.

License

MIT License