Table of Contents

• Rationale
• How to import
• Quickstart
• Roadmap
• Inspired by
• License

Rationale

When you think about it, web applications can be modeled as state machines. You should only jump from one state to another and not magically end up in another in an unpredictable manner. You should only make transitions that are possible for your current state. Modeling your web application as a state machine makes managing the flow of your application much easier as it makes your application more predictable. This is the main driving force of building this library.

How to import

Import on the browser

<script src="https://cdn.jsdelivr.net/npm/unlimited-machine-works@1.1.5/umw.min.js" async></script>

Import on Node

const UMW = require('unlimited-machine-works')

Quickstart

• Creating a machine
  • Creating a machine explained
• Checking what actions you can do
• Doing a transition
• Reacting to transitions

Creating a machine

You can use the summon or make methods to create a machine.

const machine = UMW.summon({name: 'Attack Helicopter', speed: 0}, {
  'INITIAL': {
    'MOVE': {
      to: 'MOVING',
      action: (data, args) => {
        return Object.assign({}, data, {speed: 1})
      }
    }
  },
  'MOVING': {
    'ACCELERATE': {
      to: 'MOVING',
      action: (data, args) => {
        return Object.assign({}, data, {speed: data.speed + 1})
      }
    },
    'ACCELERATE_BY': {
      to: 'MOVING',
      action: (data, args) => {
        return Object.assign({}, data, {speed: data.speed + args.speed})
      }
    },
    'STOP': {
      to: 'INITIAL',
      action: (data, args) => {
        return Object.assign({}, data, {speed: 0})
      }
    }
  }
})

Creating a Machine Explained

The first argument of creating a machine is an object that contains the initial data that you want to manage alongside your state and transitions. The second argument is optional if you don't want to add states upon machine creation. The second argument allows you to add states and transitions upon creating the machine.

Take a look at this snippet from the above code:

'INITIAL': {
  'MOVE': {
    to: 'MOVING',
    action: (data, args) => {
      return Object.assign({}, state, {speed: 1})
    }
  }
}

The INITIAL key is a state. Each state should have at least transition or else you won't be able to state. In this case, MOVE is the transition of the INITIAL state. The to key of a transition specifies to which state to go to after the transition. The action key of a transition should be a function that accepts the current data and the arguments given when the transition is called. The return value will replace the data that was originally given.

Checking what transitions you can do

You can use the actions method of your machine to check. This will return the transition names as an array of strings.

console.log(machine.actions); // [ 'MOVE' ]

Doing a transition

You can use the do method of your machine to execute a transition.

machine.do('MOVE')

If the transition defined requires additional arguments, you can add an object with the arguments as the second argument.

machine.do('ACCELERATE_BY', {speed: 4})

speed can be accessed from the args object. Check the snippet above.

Reacting to transitions

You can react to transitions by adding a subscriber to the machine using the addSubscriber method. The method takes a function which receives the new state and data after the transition. You can then do things like rendering elements in this function.

This piece of code will log the current speed data everytime a transition occurs.

machine.addSubscriber((state, data) => {
  console.log(`Speed: ${data.speed}`)
})

Graphics Credits

Logo by my sister Jade Ada (@blondiewiththebadhair).

Other Icons

Roadmap

• Create react-umw
• Using asynchronous functions for subscribers and other things
• Using Proxy objects to detect change
• Data diffing
• Adding summon() flag for verbose errors
• Adding subscribers as a part of the spec
• Move addSubscribers() in to an Adding Subscribers Dynamically section
• Add tests
• Add status badges
• Add Flow
• Add visualization

Inspired By

• Stent
• Hyperapp

License

MIT