Vo is a control flow library for minimalists

  • vo

Downloads in past


23674.0.28 years ago9 years agoMinified + gzip package size for vo in KB


Minimalist, yet complete control flow library

What you get

  • new in 4.0 Consistent function signatures
  • Tiny library (16kb minified + gzipped, common modules)
  • 2 different kinds of flows: pipeline & stack
  • Browser & server support
  • Supports promises, generators, & sync functions
  • Serial and parallel execution for every flow
  • Returns a promise that you can yield on or "await"
  • DEBUG=vo for insight into what is being called
  • Easily catch and fix errors anywhere in the pipeline
  • Errors passed as arguments so you know where the failure occurred
  • Early exit support
  • Well-tested


  • Node.js or Browserify: npm install vo
  • Standalone: vo.js & vo.min

Getting Started

Vo supports 2 kinds of asynchronous flows:
  • pipelines: Transformation pipeline. Return values become the arguments to the next function. As of 4.0.0, only the first argument to vo changes.
  • stacks: Express-style. Arguments are passed in at the top and flow through each middleware function

Both of these flows support both parallel and serial execution


function * get (url) {
  return yield fetch(url)

function map (responses) {
  return responses.map(res => res.status)

], map).then(function (statuses) {
  assert.deepEqual([ 200, 200 ])

Learn by example

There's a lot going on behind the scenes of vo, so lets take these examples one at a time:


Behaves like transform streams, where return values become arguments to the next function.
  1. single argument, executed in order
  2. multiple arguments, executed in order
  3. single argument, executed in parallel
  4. multiple arguments, executed in parallel
  5. exit early from the pipeline
  6. error in the pipeline
  7. catch error and continue
  8. pipeline composition using promises
  9. pipeline composition with generators


Behaves like express middleware, where the initial arguments are arguments to every function, regardless of return value.
Examples coming soon! Check out the comprehensive test suite for now.


Not implemented yet! Going to use Blake's excellent throwback library to implement this. Also, accepting PRs :-D

Vo Runtime

Now you can run generators top-level with the runtime:
var res = yield superagent.get('http://google.com')
console.log(res.status) // 200

vo index.js


Binding a generator function isn't implemented consistently yet
Use co-bind just to be safe.


We have a comprehensive test suite. Here's how you run it:
npm install
make test