npm package discovery and stats viewer.

Discover Tips

  • General search

    [free text search, go nuts!]

  • Package details

    pkg:[package-name]

  • User packages

    @[username]

Sponsor

Optimize Toolset

I’ve always been into building performant and accessible sites, but lately I’ve been taking it extremely seriously. So much so that I’ve been building a tool to help me optimize and monitor the sites that I build to make sure that I’m making an attempt to offer the best experience to those who visit them. If you’re into performant, accessible and SEO friendly sites, you might like it too! You can check it out at Optimize Toolset.

About

Hi, 👋, I’m Ryan Hefner  and I built this site for me, and you! The goal of this site was to provide an easy way for me to check the stats on my npm packages, both for prioritizing issues and updates, and to give me a little kick in the pants to keep up on stuff.

As I was building it, I realized that I was actually using the tool to build the tool, and figured I might as well put this out there and hopefully others will find it to be a fast and useful way to search and browse npm packages as I have.

If you’re interested in other things I’m working on, follow me on Twitter or check out the open source projects I’ve been publishing on GitHub.

I am also working on a Twitter bot for this site to tweet the most popular, newest, random packages from npm. Please follow that account now and it will start sending out packages soon–ish.

Open Software & Tools

This site wouldn’t be possible without the immense generosity and tireless efforts from the people who make contributions to the world and share their work via open source initiatives. Thank you 🙏

© 2024 – Pkg Stats / Ryan Hefner

uml-state-machine

v0.5.0

Published

UML state machine in Javascript.

Downloads

4

Readme

UML State Machine

An implemenation of the UML state machine pattern in Javascript.

  • Hierarchical
  • onEntry onExit function
  • Observable

Install

npm install uml-state-machine --save

Usage

Here is the hello word of finite state machine: a light switch:

  • 2 events: evOn and evOff.
  • 2 states: Off and On.
  • 2 actions: light.doOff() and light.doOn().

State machine diagram describing the light switch:

alt text


const stateMachineDefinition = {
  name: "LightSwitch",
  events: ["evOn", "evOff"],
  state: {
    states: {
      "Off": {
        onEntry: light => light.doOff(),
        transitions: [{
          event: "evOn",
          nextState: "On",
          actions:[
            light => light.log("starting on")
          ]
        }]
      },
      "On": {
        onEntry: light => light.doOn(),
        transitions: [{
          event: "evOff",
          nextState: "Off",
          actions:[
            light => light.log("starting off")
          ]
        }]
      }
    }
  }
}

const light = Light();

const machine = Machine({
  definition: stateMachineDefinition,
  actioner: light
});

machine.enterInitialState();
machine.evOff();
machine.evOn();

Hierarchical example

Hierarchical state machine allows to model state as a tree, the goal is to gather states that share common transitions. When transitioning from one state to another, a chain of onExit and onEntry functions is called.

alt text

const smDef = {
  name: "Hierarchical",
  events: ["evOn", "evOff"],
  state: {
    transitions: [{event:"evOn", nextState:"S2_3"}],
    states: {
      "S1": {
        states:{
          "S1_1":{},
          "S1_2":{
            states:{
              "S1_2_1":{},
              "S1_2_2":{}
            }
          }
        }
      },
      "S2":{
        states:{
          "S2_1":{},
          "S2_2":{},
          "S2_3":{}
        }
      }
    }
  }
}

const machine = Machine({
  definition: smDef
});

machine.enterInitialState();
/*
onEntry  S
onEntry  S1
onEntry  S1_1
*/
machine.evOn()
/*

onTransitionBegin  S1_1 S2_3
onExit  S1_1
onExit  S1
onEntry  S2
onEntry  S2_3
onTransitionEnd  S1_1 S2_3
*/

Observable

To find out what's going on inside the state mahine, customs observers can be attached.

Below is an example of a simple observer that logs when a state enters or exits, and when a transition begins and ends.


const machine = Machine({
  definition: smDef,
  observers: {
    onEntry(context, stateName) {
      console.log("onEntry ", stateName)
    },
    onExit(context, stateName) {
      console.log("onExit ", stateName)
    },
    onTransitionBegin(context, statePrevious, stateNext) {
      console.log("onTransitionBegin ", statePrevious, stateNext)
    },
    onTransitionEnd(context, statePrevious, stateNext) {
      console.log("onTransitionEnd ", statePrevious, stateNext)
    }
  }
});