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autoflow (formerly react) is a javascript module to make it easier to work with asynchronous code, by reducing boilerplate code and improving error and exception handling while allowing variable and task dependencies when defining flow.
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React is a javascript module to make it easier to work with asynchronous code, by reducing boilerplate code and improving error and exception handling while allowing variable and task dependencies when defining flow. This project is applying the concepts of Reactive programming or Dataflow to controlling application flow.

This async flow control module is initially designed to work with Node.js but is planned to be extended to browser and other environments.

React gets its name from similarities with how "chain reactions" work in the physical world. You start the reaction and then it cascades and continues until complete.

Also "Reactive Programming" or "Dataflow" describe defining flow which reacts to the data similar to how a spreadsheet updates cells. These are good examples of how React controls flow based on when data is available

It takes inspiration from several projects including:


  • Minimize boilerplate code needed for working with asynchronous functions
  • Minimize the need to customize your code simply to use async flow control. The use of a flow control module ideally should not affect the way you write your code, it should only help take over some of the burden.
  • Improved error and exception handling
  • Provide useful stack traces and context information for easier debugging
  • Make code more readable and easier to understand which should translate to less defects
  • Provide the right level of abstraction to make it easier to refactor code, without being too magical
  • Allow the mixing of pure functions, method calls, and callback style functions in the flow


  • async node-style callback(err, arg...) functions
  • sync functions which directly return value
  • object instance method calls
  • class method calls
  • selectFirst flow where the first task that returns defined, non-null value is used
  • promise style functions - also automatic resolution of promise inputs (optional require('react/promise-resolve');)
  • (planned) use of resulting flow function as callback style or promise style (if no callback provided)
  • (planned) iteration on arrays, streams, sockets
  • (planned) event emitter integration

The tasks can be mixed, meaning you can use async, sync, object method calls, class method calls, etc in the same flow.


Borrowing heavily from Tim and Elijah's ideas for conductor, this async flow control module provides a way to construct a flow from a collection of functions or methods (referred to as tasks in this module). It allows dependencies to be defined between the tasks so they can run in parallel as their dependencies are satisfied. React can us both variable dependencies and task dependencies.

As tasks complete, React watches the dependencies and kicks off additional tasks that have all their dependencies met and are ready to execute. This allows the flow to run at maximum speed without needing to arbitrarily block tasks into groups of parallel and serial flow.

To reduce the boilerplate code needed and improve error handling, React automatically provides callback functions for your asynchronous code. These React-provided callback functions perform these steps:

  1. check for error and handle by calling outer callback function with this error after augmenting it with additional context information for easier debugging
  2. save the callback variables into a context for future reference
  3. call back into React (and it will kick off additional tasks that are now ready to go)


  • Parse and validate DSL rules at module load time
  • Validate the flow AST at module load time - determine if dependencies can all be met as defined
  • Execute the flow AST by calling the function with arguments


npm install react


Pull from github -


  1. Default DSL
  2. Direct AST
  3. Using pseudocode DSL
  4. Using jquery-like chaining DSL

These live in the examples folder so they are ready to run. Also see test/module-use.test.js for more examples as well as the specific tests for the DSL you want to use.

Example using default DSL

// in your foo module
var react = require('react');

// some normal async and sync functions
function loadUser(uid, cb){ }
function loadFile(filename, cb){ }
function markdown(filedata) { }
function writeOutput(html, user, cb){  }
function loadEmailTemplate(cb) { }
function customizeEmail(user, emailHtml, cb) { }
function deliverEmail(custEmailHtml, cb) { }

// define fn, glue together with react, it will parallelize
// starts with name and in/out params, then the tasks
var loadAndSend = react('loadAndSend', 'uid, filename, cb -> err, user',
  loadUser, 'uid, cb -> err, user',
  loadFile, 'filename, cb -> err, filemd',
  markdown, 'filemd -> html',  // no cb, implies sync fn
  writeOutput, 'html, user, cb -> err, htmlBytesWritten',
  loadEmailTemplate, 'cb -> err, emailmd',
  markdown, 'emailmd -> emailHtml',  // no cb, implies sync fn
  customizeEmail, 'user, emailHtml, cb -> err, custEHtml',
  deliverEmail, 'custEHtml, cb -> err, custBytesWritten'
exports.loadAndSend = loadAndSend; // is a normal fn created by react

// in a different module far far away, use this as any other node function
var foo = require('foo');
foo.loadAndSend(100, '', function (err, user) {
  // tasks were parallelized based on their depedencies

Example directly using AST

var react = require('react');

function load(res, cb) { setTimeout(cb, 100, null, res + '-loaded'); }
function prefix(prefstr, str, cb) { setTimeout(cb, 100, null, prefstr + str); }
function postfix(str, poststr, cb) { setTimeout(cb, 100, null, str + poststr); }
function upper(str) { return str.toUpperCase(); }

var fn = react();
var errors = fn.setAndValidateAST({
  inParams: ['res', 'prefstr', 'poststr'],
  tasks: [
    { f: load,    a: ['res'],              out: ['lres'] },
    { f: upper,   a: ['lres'],             out: ['ulres'], type: 'ret'  },
    { f: prefix,  a: ['prefstr', 'ulres'], out: ['plres'] },
    { f: postfix, a: ['plres', 'poststr'], out: ['plresp'] }
  outTask: { a: ['plresp'] }
console.error('errors:', errors); // []

fn('foo', 'pre-', '-post', function cb(err, lres) {
  console.error('err:', err);  // null
  console.error('lres:', lres); // pre-FOO-LOADED-post

Example using Function String DSL interface

var fstrDefine = require('react/dsl/fstr');

function loadUser(uid, cb){ setTimeout(cb, 100, null, "User"+uid); }
function loadFile(filename, cb){ setTimeout(cb, 100, null, 'Filedata'+filename); }
function markdown(filedata) { return 'html'+filedata; }
function prepareDirectory(outDirname, cb){ setTimeout(cb, 200, null, 'dircreated-'+outDirname); }
function writeOutput(html, user, cb){  setTimeout(cb, 300, null, html+'_bytesWritten'); }
function loadEmailTemplate(cb) { setTimeout(cb, 50, null, 'emailmd'); }
function customizeEmail(user, emailHtml, cb) { return 'cust-'+user+emailHtml; }
function deliverEmail(custEmailHtml, cb) { setTimeout(cb, 100, null, 'delivered-'+custEmailHtml); }

function useHtml(err, html, user, bytesWritten) {
  if(err) {
    console.log('***Error: %s', err);
  console.log('final result: %s, user: %s, written:%s', html, user, bytesWritten);

var loadAndSave = fstrDefine('filename, uid, outDirname, cb', [  // input params
  loadUser,         'uid              -> err, user',     // calling async fn loadUser with uid, callback is called with err and user
  loadFile,         'filename         -> err, filedata',
  markdown,         'filedata         -> returns html',    // using a sync function
  prepareDirectory, 'outDirname       -> err, dircreated',
  writeOutput,      'html, user       -> err, bytesWritten', { after: prepareDirectory },  // only after prepareDirectory done
  loadEmailTemplate, '                 -> err, emailmd',
  markdown,         'emailmd          -> returns emailHtml',   // using a sync function
  customizeEmail,   'user, emailHtml  -> returns custEmailHtml',
  deliverEmail,     'custEmailHtml    -> err, deliveredEmail', { after: writeOutput }  // only after writeOutput is done
], 'err, html, user, bytesWritten');   // callback output params

loadAndSave('', 100, '/tmp/foo', useHtml);  // executing the flow

Example using pseudocode DSL interface

var pcodeDefine = require('react/dsl/pcode');

function multiply(a, b, cb) { cb(null, a * b); }
function add(a, b) { return a + b; }
var locals = {   // since pcodeDefine uses strings, need references to functions passed into react
  multiply: multiply,
  add: add

var fn = pcodeDefine('a, b, cb', [  // input params
  'm := multiply(a, b)',   // using a callback function, use :=
  's = add(m, a)',        // using a sync function, use =
  'cb(err, m, s)'     // output params for final callback
], locals);    // hash of functions that will be used

fn(2, 3, function (err, m, s) {
  console.error('err:', err); // null
  console.error('m:', m);  // 2 * 3 = 6
  console.error('s:', s);  // 6 + 2 = 8

Example using jquery-like chaining DSL interface

var chainDefine = require('react/dsl/chain');

function multiply(a, b, cb) { cb(null, a * b); }
function add(a, b) { return a + b; }

var fn = chainDefine()
  .in('a', 'b', 'cb')                                   // input params
  .out('err', 'm', 's')                                 // final callback output params
  .async(multiply).in('a', 'b', 'cb').out('err', 'm')   // task def - async fn, in params, callback out params
  .sync(add).in('m', 'a').out('s')                      // task def - sync fn, in params, return value

fn(2, 3, function (err, m, s) {
  console.error('err:', err); // null
  console.error('m:', m);  // 2 * 3 = 6
  console.error('s:', s);  // 6 + 2 = 8


  • 2012-01-13 - Add promise tasks, promise resolution, refactor alternate DSL interfaces as optional requires (v0.2.7)
  • 2012-01-11 - Provide warning/error when name is skipped in default DSL, literal check in validate (v0.2.5)
  • 2012-01-10 - Create default DSL for react(), create error for missing variables, list remaining tasks when flow won't complete
  • 2011-12-21 - Refactor from ground up with tests, changes to the interfaces
  • 2011-10-26 - React is in active development and interface may change frequently in these early stages. Current code is functional but does not perform validation yet. Additional interfaces are planned to make it easy to define flows in a variety of ways. Documentation and examples forthcoming.

Test Results

ok ast.test.js .................... 10/10
ok cb-task.test.js ................ 31/31
ok chain.test.js .................. 59/59
ok core.test.js ................... 98/98
ok dsl.test.js .................... 63/63
ok event-manager.test.js .......... 13/13
ok exec-options.test.js ............. 3/3
ok finalcb-task.test.js ............. 5/5
ok fstr.test.js ................... 67/67
ok input-parser.test.js ........... 15/15
ok module-use.test.js ............. 64/64
ok pcode.test.js .................. 68/68
ok ret-task.test.js ............... 31/31
ok task.test.js ..................... 1/1
ok validate-cb-task.test.js ......... 6/6
ok validate-ret-task.test.js ........ 7/7
ok validate.test.js ............... 31/31
ok vcon.test.js ................... 42/42
total ........................... 632/632




  • Author: Jeff Barczewski (@jeffbski)


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