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Communicating sequential processes for node. Go style concurrency with channels.

WARNING: This package is at an experimental stage at the moment.


This package requires ES6 generators which are switched on in node 0.11.6 through passing the -harmony flag to the node interpreter.


$ npm i csp


$ node -harmony <file>.js


// Concurrent prime sieve. 
var csp = require("csp");
var generate = function (n) {
  return function* (ch) {
    for (var i = 2; i < n; i++) {
      yield ch.put(i);
var filter = function* (inc, out, prime) {
  for (;;) {
    var i = yield inc.take();
    if (% prime != 0) {
      yield out.put(i);
csp.spawn(function* () {
  var ch = new csp.Chan();
  yield csp.spawn(generate(1000), ch);
  for (var i = 0; i < 10; i++) {
    var prime = yield ch.take();
    ch1 = new csp.Chan();
    yield csp.spawn(filter, ch, ch1, prime);
    ch = ch1;


(yield) spawn(*gen, arg1 ... argN)

Create a new process from gen and pass arguments arg1 ... argN to it. If prefixed by yield the process will be managed by the outer process and will be destroyed when the outer process quits.

new Chan(size = 0)

Create a new channel with buffering size.

yield Chan.prototype.put(val)

Send val on the channel and depending on the channels buffering either block or move on.

yield Chan.prototype.take() = val

Block until a value is sent on the channel and return that value as val.

yield wait(ms)

Block for ms milliseconds.

yield select(chan1 ... chanN) = chan

Block until a value is sent on one of chan1 ... chanN and then return that channel as chan. Important to note that select does not issue a take on the channel, you have to do this yourself.

yield quit()

Forcefully quit the current process.

wrap(fn(arg1 ... argN, cb(err, val)))

Take a function that uses node's usual callback convention and return one that blocks until it is finished.

chanify(fn(arg1 ... argN, cb(err, val)), chan)

Take a function that uses node's usual callback convention and return one that sends a value on channel chan when it is finished.