join2Async, could be easily expanded to N-size. looked useful but then didn't solve the problem. dumping here so I may use it when in need. hopefully this makes it easier to find: join queue parallel asynchronous synchronous add flush empty enqueue dequeue

gistfile1.js

/* this queue-style thing accepts a callback
    and calls it when it has two results attached
    usage:
      j2a = new join2Async(console.log);
      setTimeout( 'j2a.addResult("foo")', Math.ceil(Math.random()*10));
      setTimeout( 'j2a.addResult("var")', Math.ceil(Math.random()*10));
      // enjoy the race and see who's first \o/
    */
    function join2Async(cb) {
    // join 2 async call and return once *both* are done.
      this.firstResult = null;
      this.callBack = cb;
    }
    join2Async.prototype = {
      addResult: function add(res) {
        if ( this.firstResult === null) {
          this.firstResult = res;
        }
        else { this.callBack( [this.firstResult, res] ) }
      }
    }