join_promises.js

// join any number of promises and return the results in the order they were passed in
function join_promises () {
  var p = make_promise(),
    args = Array.prototype.slice.call(arguments,0),
    num = 0,
    ps = [];

    // Debug version only
    if (args[0].isArray) {
      if (args.length > 1) {
        var msg = "Multiple arrays of promises not supported";
        DBG(msg);
        throw msg;
      }
      //args = args[0];
    }

    // Production version
    args = (args[0].isArray ? args[0] : args);
    num = args.length;
    args.forEach(function (el, i, arr) {
      // increase the array to the appropriate size
      ps.push(undefined);
      el.when(function (data) {
        ps[i] = data;
        num -= 1;
        DBG(JSON.stringify(args) + ' ' + ps[i] + ' ' + num + ' ' + i );
        if (0 === num) {
          DBG('Result: ' + JSON.stringify(ps));
          p.fulfill.apply(p, ps);
          // p.fulfill.call(p, ps);
        }
      });
    });
  return p;
}