z

z.js

//
// an experimental flow control library.
// please dont ever use this for anything.
//

var z = function z(f) {

  if (!(this instanceof z)) { 
    return new z(f); 
  }
  this.f = f;
};

z.iterator = function(f) { z.itr = f; };

z.array = function(a) { z.arr = a; };

z.done = function(f) { z.dn = f; };

z.done.valueOf = function() {
  z.arr.forEach(function(i) {
    var done = function() {
      z.completed += 1;
      if (z.completed === z.arr.length) {
        z.dn();
      }
    }

    if (z.itr) {
      z.itr(i, done);
    }
    else {
      i(done);
    }
  });
  z.itr = null;
  z.completed = 0;
  z.arr = [];
};

z.arr = [];

z.completed = 0;

z.prototype.valueOf = function() {
  z.arr.push(this.f);
}

//
// call an iterator for every item in the array
// and then when they have all completed call the
// done function.
//
z.array(['foo', 'bar']);
z.iterator(function(val, next) { console.log(val); next(); });
z.done(function(err) { console.log('DONE-A'); });

z.array >> z.done;

//
// call all functions until they are all done, then
// call a final function.
//
var a = z(function(next) { console.log('A'); next(); });
var b = z(function(next) { console.log('B'); next(); });

z.done(function(err) { console.log('DONE-B'); });

a >> b >> z.done;

Since lots of people are asking, I'd like to iterate; don't use this for anything. I just wrote this to explain to someone how valueOf works.

z(function(next) { console.log('A'); next(); })
>> z(function(next) { console.log('B'); next(); })
>> z.done(function(err) { console.log('DONE-B'); })