noflo

NoFlo: Flow-based programming for JavaScript

NoFlo is an implementation of flow-based programming for JavaScript running on both Node.js and the browser. From WikiPedia:

In computer science, flow-based programming (FBP) is a programming paradigm that defines applications as networks of "black box" processes, which exchange data across predefined connections by message passing, where the connections are specified externally to the processes. These black box processes can be reconnected endlessly to form different applications without having to be changed internally. FBP is thus naturally component-oriented.

Developers used to the Unix philosophy should be immediately familiar with FBP:

This is the Unix philosophy: Write programs that do one thing and do it well. Write programs to work together. Write programs to handle text streams, because that is a universal interface.

It also fits well in Alan Kay's original idea of object-oriented programming:

I thought of objects being like biological cells and/or individual computers on a network, only able to communicate with messages (so messaging came at the very beginning -- it took a while to see how to do messaging in a programming language efficiently enough to be useful).

NoFlo components can be written in any language that transpiles down to JavaScript, including ES6. The system is heavily inspired by J. Paul Morrison's book Flow-Based Programming.

Read more at https://noflojs.org/.

Suitability

NoFlo is not a web framework or a UI toolkit. It is a way to coordinate and reorganize data flow in any JavaScript application. As such, it can be used for whatever purpose JavaScript can be used for. We know of NoFlo being used for anything from building web servers and build tools, to coordinating events inside GUI applications, driving robots, or building Internet-connected art installations.

Tools and ecosystem

NoFlo itself is just a library for implementing flow-based programs in JavaScript. There is an ecosystem of tools around NoFlo and the fbp protocol that make it more powerful. Here are some of them:

• Flowhub -- browser-based visual programming IDE for NoFlo and other flow-based systems
• noflo-nodejs -- command-line interface for running NoFlo programs on Node.js
• MsgFlo -- for running NoFlo and other FBP runtimes as a distributed system
• fbp-spec -- data-driven tests for NoFlo and other FBP environments
• flowtrace -- tool for retroactive debugging of NoFlo programs. Supports visual replay with Flowhub

See also the list of reusable NoFlo modules on NPM.

Requirements and installing

NoFlo is available for Node.js via NPM, so you can install it with:

$ npm install noflo --save

You can make a browser build of NoFlo using webpack. The grunt-noflo-browser plugin makes this easy.

Installing from Git

NoFlo requires a reasonably recent version of Node.js, and some npm packages. Ensure you have the grunt-cli package installed (grunt command should be available on command line) and NoFlo checked out from Git. Build NoFlo with:

$ grunt build

You can also build NoFlo only for the desired target platform with either grunt build:nodejs or grunt build:browser.

Then you can install everything needed by a simple:

$ npm link

NoFlo is available from GitHub under the MIT license.

Changes

Please refer to the Release Notes and the CHANGES.md document.

Usage

Please refer to http://noflojs.org/documentation/. For visual programming with NoFlo, see https://docs.flowhub.io/.

Development

NoFlo development happens on GitHub. Just fork the main repository, make modifications and send a pull request.

We have an extensive suite of tests available for NoFlo. Run them with:

$ npm test

Platform-specific tests

By default, the tests are run for both Node.js and the browser. You can also run only the tests for a particular target platform:

$ grunt test:nodejs

or:

$ grunt test:browser

Running tests automatically

The build system used for NoFlo is also able to watch for changes in the filesystem and run the tests automatically when something changes. To start the watcher, run:

$ grunt watch

If you want to only run a particular part of the test suite, you can filter them using the TESTS environment variable:

$ TESTS="Network Lifecycle" grunt watch

To quit thew watcher, just end the process with Ctrl-C.

Discussion

There is an IRC channel #fbp on FreeNode, and questions can be posted with the noflo tag on Stack Overflow. See http://noflojs.org/support/ for other ways to get in touch.

Changelog

0.8.5 (September 17th 2017)

• It is now possible to set individual ports to unscoped mode by setting the scoped: false parameter. This is useful for components that mix unscoped and scoped inputs
• Ports and IP objects can now be annotated with a JSON schema for their payloads using the schema key. Ports with a schema annotate their IP objects automatically with the schema unless the IP object already has a specific schema
• The previous type key of ports is now converted to the schema key. The schema of a port is available via the getSchema() method