jWorkflow

Dude, where is my workflow?

jWorkflow is a workflow engine for JavaScript that provides the ability to create workflows to chain methods together in an easy to understand syntax:

var fooodOrder = jWorkflow.order(garlicChicken)
                          .andThen(whiteRice)
                          .andThen(wontonSoup)
                          .andThen(cookiesFortune)
                          .andThen(noAndThen)
                          .andThen(noAndThen)
                          .andThen(noAndThen)
                          .andThen(noAndThen);

fooodOrder.start();

Install

jWorkflow can be used in node or included in the browser. It can be installed with npm

npm install jWorkflow

and used

var jWorkflow = require("jWorkflow");

or just include jWorkflow.js in your webpage and use window.jWorkflow.

Usage

jWorkflow orders are started with a call to jWorkflow.order:

function dude() {
    // some of the best code in the world will live here
}

var order = jWorkflow.order(dude);

// orders can also be started with no initial function
var pizzacoli = jWorkflow.order();

jWorkflow tasks at the root are just functions that will be invoked in the order they are built. Any number of tasks can be then appended to the order:

order.andThen(sweet).andThen(dude).andThen(sweet);

The functions passed into the order will not be invoked until you call:

order.start();

The context to be used when invoking the functions can be passed in while creating the order:

order.andThen(transfunctioner.photonAcceleratorAnnihilationBeam, transfunctioner);

An initial value can be passed into the start method to seed the first function:

order.start({
    initialValue: 10
});

Passing Values between tasks

jWorkflow tasks can access the return value of the previous task with the previous parameter:

function meaningOfLife() {
   //find the meaning of life
   return 42; 
}

function writeBook(previous) {
   console.log("the meaning of life is " + previous);
}

var guide = jWorkflow.order(meaningOfLife).andThen(writeBook);
guide.start();

Handling Async calls

Sometimes(probably all the time) you will need to do something async when working with tasks, jWorkflow provides the ability to control the execution of the workflow via a baton that is passed to the task

function procrastinate(previous, baton) {
    //take the baton, this means the next task will not run until you pass the baton
    baton.take();

    window.setTimeout(function() {
        //do some stuff

        //please be nice and always remember to pass the baton!
        baton.pass();
    }, 1000);
}

If you want to pass a return value to the next task you can pass it along with the baton.

NOTE: if you did take the baton, the return value from your function will NOT be passed to the next task:

function awesometown(previous, baton) {
    baton.take();

    window.setTimeout(function() {
        
        //do stuff
        
        baton.pass(420);    //This value will be passed to the next task
    }, 100);

    return 50; // this will NOT be passed to the next function since you took the baton.
}

the start method provides a callback to execute when the workflow is finished. The final return value is also passed to the callback:

order.start({ callback: function(review) { console.log("dude!, your car is behind that mail truck!"); expect(review).toBe("two thumbs up"); } });

you can also pass context to use for the callback:

order.start({ callback: function() { //do stuff }, context: transfunctioner });

Waiting between tasks

If you ever need to take a break and reflect on the moment you can add some time(in ms) to chill between tasks:

jWorkflow.order(seeDoubleRainbow)
         .chill(1000)
         .andThen(omg)
         .andThen(omg)
         .andThen(omg)
         .chill(1000)
         .andThen(freakOut);

Handling Parallel tasks

If you need to handle some tasks and don't care about when they are done you can pass in an array of functions and / or other workflows to execute at the same time.

jWorkflow.order([man, man, halfMan])
         .andThen([jWorkflow.order([guy, guy]).andThen(girl), pizzaPlace]);

Canceling Workflows

To cancel the execution of the workflow you can call the drop method on the baton:

function (previous, baton) {
    //the value passed to drop will be passed onto the final callback if it exists
    baton.drop("I dropped the soap");
    //this value will NOT be passed to the next workflow step
    return 10;
}

NOTE: This will force the workflow into async mode.

Contributers:

Gord Tanner <[email protected]>