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

See also

EasyFlow for Java

License

ISC License (ISC)

Copyright (c) 2015, Andrey Chausenko andrey.chausenko@gmail.com

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.

THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.