Plans async flow controller

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Plans is a fast, powerful flow control library which combines the syntactic sugar and chaining of promises with the speed of simple callbacks. It accepts synchronous and asynchronous functions, and runs them in series or parallel in limitless combinations. Plans handles errors and accepts reusable plan objects that can specify things like:

  • Success, failure and completion functions
  • Timeouts
  • Retries with delays and backoffs
  • HTTP responses
  • Reusable base plans for fallback

Plans helps you do more, faster, with less code and greater reliability.

Quick Start

Install plans in your project:

npm install --save plans

Require plans in a script:

var plans = require('plans');

Use plans:

// Flow values through an array of functions.
var file = 'package.json';
plans.flow(file, [fs.readFile, JSON.parse])
  .then(function (data) {'This package is called "' + + '".');
  function (e, filename) {
    console.error('Failed to read "' + file + '".', e);

A plan can have a success or failure function:, {
  ok: function (value) {"Success!", value);
  fail: function (error) {
    console.error("Failure.", error);

Or an "errback", if that's your thing:, {
  done: function (error, value) {
    if (error) {"Success!", value);
    } else {
      console.error("Failure.", error);

Anything can be a plan, assuming it exposes methods like ok, info, fail, error or done. Since the console object has info and error methods, it can be used to show the value or the error that a function generates:, console);

Plans can chain:

  .then(function (json) {"Package JSON:
" + json);
  function (error) {
    console.error("These aren't the droids you're looking for...", error);

Or run all functions in parallel:

plans.all([fn1, fn2, fn3], console);

Or run each function in series:

plans.each([fn1, fn2, fn3], console);

And much more:

var path = "package.json";
var version = "1.0.0";
plans(path).flow([fs.readFile, JSON.parse], {
  ok: function (pkg) {"Package name: " + + ".");
  fail: function (e) {
    console.error("Failed to read " + process.cwd() + "/" + e.input + ".", e);
  SyntaxError: function (e) {
    console.error("Failed to parse JSON:", e.input, e);
.andRun(function (pkg) {
  pkg.version = version; // U-P-G-R-A-Y-E-D-D?
  return pkg;
.args(function (json) {
  return [path, json];
.run(fs.writeFile, {
  ok: function () {"We're at v" + version + "!");


This documentation uses internally-standardized terms to describe abstract concepts. Hopefully, this mapping will help.

  • args - an array or an arguments object (i.e. anything with a zero-indexed set of properties an integer property called length).
  • base - a plan whose properties are used in place of any properties that do not exist on a run's plan.
  • chain - an instance of Plans.chain, which links a run to its children and exposes chaining methods like then.
  • collection - an input which is either array-flavored or object-flavored. The former uses indexes as keys, and the latter uses properties as keys.
  • fns - a function or array of functions, which can operate synchronously by returning a value other than undefined, or asynchronously by passing a value to a callback.
  • input - a value that belongs to a chain and comes in one of 3 flavors: data, map or list. The latter 2 flavors can send output through multiple chains.
  • keys - numbers or strings used to map inputs to outputs.
  • run - an object created from arguments to a plans method, used to store the input, state and value.
  • state - a phase of chain processing. 0 means waiting. 1 means succeeded. 2 means failed. 3 means the chain was created just to provide input to child runs.
  • value - an instance of Error if a run failed, or a non-error value if a run succeeded.


The plans API consists of methods for running and chaining functions, and plans itself is a function that returns new chains.

So you can create a chain with "Hi!" as input, and log it:



Creates a chain with data-flavored input to use in one call.


Creates a chain with map-flavored input to use in parallel.


Creates a chain with list-flavored input to use in series.

args([object], array)

Creates a chain with args-flavored input to be applied to functions, optionally using object as the this context when arguments are applied.

run(fn, [plan])

Run a single function, according to a plan.

all(fns, [plan])

Run all functions in parallel, according to a plan.

each(fns, [plan])

Run each function in series, according to a plan.

flow(fns, [plan])

Run functions in serial, passing each value as input to the next function.

filter(fns, [plan])

Run all functions on the input, generating a value composed of input items which resulted in truthy, non-error results from every function.


No-op function, used to replace callbacks where necessary.

Plan Objects

A plan is an object or function which specifies how you would like to handle a result or an error, and all plans methods accept a plan argument. A plan can be saved and reused for multiple plans method calls, making it easy to do things like building retry/backoff/timeout/failure handling into all of your application's external service calls, while conserving resources and code.

Plan objects specify their behavior by having methods such as ok and error:

var plan = {
  ok: function (result) {'Success! :)', result);
  error: function (error) {
    console.error('An error occurred. :(', error);
  done: function (error, result) {

If a function is used as a plan, it gets called with the arguments that an "errback" expects.

Base Plans

The plans.base object is used as a plan whenever an optional plan argument is omitted from a run. In addition, plans.base is used as the base for any plan that does not have its own base property.

By default, plans.base just handles failures by logging errors to the console. But if you'd rather fail silently, you can:

plans.base = null;

Or you can make your own base plan do whatever you need it to do:

plans.base = {

  retries: 2, // 3rd time's the charm.

  delay: 1e3, // Wait a sec.

  backoff: 2, // Then wait 2 secs.

  timeout: 1e4, // 10 seconds without a result is no good.

  // Handle success.
  ok: function (value) {
    console.log('OK: ', value);

  // Handle failure.
  error: function (error) {
    console.log('Uh-ok: ', error);

Plan Properties

A plan can have many properties to control its behavior and handle results. Every property is optional, and the base is used for any property whose value is undefined.

ok: function (value) {...}

Called when there is no error. Its argument is the return value of the run.

Note: For console support, info works in place of ok.

fail: function (error) {...}

Called when an error occurred. Its argument is the first error that occurred.

Note: For console support, error works in place of fail.

fails: function (array) {...}

Called when one or more errors occurred. If a plan has both .error and .errors, they will both be called when an error occurs, and each of them will only be called once (per usage).

done: function (error, result) {...}

Called when execution has finished. If execution failed, the error is passed as the first argument, otherwise the result is passed as the second argument.

retries: integer

The number of times to re-run before failing. If all retries fail, the plan's failure methods will be called. Note: The initial run is not counted in this number, so for example, setting retries to 2 would result in 3 tries total before failing.

delay: milliseconds

The number of milliseconds to wait before retrying (default: 0). If backoff is set to a number other than 1, then delay will be modified after the first retry.

backoff: number

A multiplier to be applied to delay after each retry, enabling exponential backoff.

timeout: milliseconds

The maximum time in milliseconds that to wait before retrying or failing. When a run times out with no retries remaining, the plan fails with a TimeoutError.

base: plan

A plan to fall back on, instead of using plans.base.

response: http.ServerResponse

The response property is used to respond to an HTTP request with a 500 error. This is done using the error property if present.

Chain Objects

Instances of plans.Chain can be used to start child runs after the parent run has ended, or to preload a run with an input.


We would like to thank all of the amazing people who use, support, promote, enhance, document, patch, and submit comments & issues. Plans couldn't exist without you.

Additionally, huge thanks go to TUNE for employing and supporting Plans project maintainers, and for being an epically awesome place to work (and play).

MIT License

Copyright (c) 2014 Sam Eubank

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.


How to Contribute

We welcome contributions from the community and are happy to have them. Please follow this guide when logging issues or making code changes.

Logging Issues

All issues should be created using the new issue form. Please describe the issue including steps to reproduce. Also, make sure to indicate the version that has the issue.

Changing Code

Code changes are welcome and encouraged! Please follow our process:

  1. Fork the repository on GitHub.
  2. Fix the issue ensuring that your code follows the style guide.
  3. Add tests for your new code, ensuring that you have 100% code coverage. (If necessary, we can help you reach 100% prior to merging.)
    • Run npm test to run tests quickly, without testing coverage.
    • Run npm run cover to test coverage and generate a report.
    • Run npm run report to open the coverage report you generated.
  4. Pull requests should be made to the master branch.

Contributor Code of Conduct

As contributors and maintainers of Plans, we pledge to respect all people who contribute through reporting issues, posting feature requests, updating documentation, submitting pull requests or patches, and other activities.

If any participant in this project has issues or takes exception with a contribution, they are obligated to provide constructive feedback and never resort to personal attacks, trolling, public or private harassment, insults, or other unprofessional conduct.

Project maintainers have the right and responsibility to remove, edit, or reject comments, commits, code, edits, issues, and other contributions that are not aligned with this Code of Conduct. Project maintainers who do not follow the Code of Conduct may be removed from the project team.

Instances of abusive, harassing, or otherwise unacceptable behavior may be reported by opening an issue or contacting one or more of the project maintainers.

We promise to extend courtesy and respect to everyone involved in this project regardless of gender, gender identity, sexual orientation, ability or disability, ethnicity, religion, age, location, native language, or level of experience.

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