Awesome

node-easy-flow

Simple and easy to use Finite State Machine (FSM) for Node.js (similar to EasyFlow for Java).

This library greatly simplifies development of asynchronous event-driven applications.

Thanks to its convenient hierarchical transition builder, logic of complex applications remains clear and application itself manageable.

Usecase for node-easy-flow is somehow similar to async.series() or async.waterfall() (see here), only node-easy-flow is more suitable for handling complex, non-linear logic.

Install

Install locally

npm install node-easy-flow

Version 2 notes

node-easy-flow has recently been updated to version 2 which is not completely backward-compatible. If you want to keep using version 1, please use this require statement

var EasyFlow = require('node-easy-flow/lib/easy-flow-v1');

and refer to v1 docs. Rest of the document describes node-easy-flow version 2.

Quick start

node-easy-flow version 2 is built using TypeScript to be used in TypeScript projects (even though is can be used with JavaScript as well). FSM is defined with node-easy-flow through combination of transitions and handlers

import { EasyFlow, from, on, to, finish, whenEnter } from 'node-easy-flow';

class AtmFlow extends EasyFlow {
    constructor() {
        super();

        // states
        const SHOWING_WELCOME = 'SHOWING_WELCOME',
            WAITING_FOR_PIN = 'WAITING_FOR_PIN',
            CHECKING_PIN = 'CHECKING_PIN',
            SHOWING_MAIN_MENU = 'SHOWING_MAIN_MENU',
            SHOWING_BALANCE = 'SHOWING_BALANCE',
            ...

        // events
        const cardPresent = 'cardPresent',
            pinProvided = 'pinProvided',
            pinValid = 'pinValid',
            pinInvalid = 'pinInvalid',
            cancel = 'cancel',
            menuShowBalance = 'menuShowBalance',
            switchOff = 'switchOff',
            ...

        // transition definitions
        from(SHOWING_WELCOME,
            on(cardPresent, to(WAITING_FOR_PIN,
                on(pinProvided, to(CHECKING_PIN,
                    on(pinValid, to(SHOWING_MAIN_MENU,
                        on(menuShowBalance, to(SHOWING_BALANCE,
                            on(cancel, to(SHOWING_MAIN_MENU))
                        )),
                        ...
                    )),
                    ...
                )),
                ...
            )),
            ...
        );

        // handler definitions
        whenEnter(SHOWING_WELCOME, (context) => {
            console.log('\n\n*** Welcome ***\n');
            context.invalidPinCounter = 0;
            rl.question('Select your option and press [Enter]...\n 1 Insert card\n 2 Terminate ATM\n', (option) => {
                this.trigger(option == 1 ? cardPresent : switchOff, context);
            });
        });

        whenEnter(WAITING_FOR_PIN, (context) => {
            console.log('\n\n*** Waiting for PIN ***\n');
            rl.question('Please enter your PIN and press [Enter] or just press [Enter] to cancel (current PIN is 1234)...\n', (pin) => {
                if (pin.length === 4) {
                    context.pin = pin;
                    this.trigger(pinProvided, context);
                } else {
                    this.trigger(cancel, context);
                }
            });
        });

        whenEnter(CHECKING_PIN, (context) => {
            if (context.pin == 1234) {
                this.trigger(pinValid, context);
            } else {
                context.invalidPinCounter = context.invalidPinCounter + 1 || 1;
                this.trigger(pinInvalid, context);
            }
        });

        ...
    }
}

Then it can be started using context object


let flow = new AtmFlow();
flow.start({ balance: 1000 });

See full example here

License

ISC License (ISC)

Permission to use, copy, modify, and/or distribute this software for any purpose with or without fee is hereby granted, provided that the above copyright notice and this permission notice appear in all copies.