循环异步调用

after.js

var After = function (callback) {
  this.index = 0;
  this.counter = 0;
  this.results = [];
  this.callback = callback;
};

After.prototype.group = function (callback) {
  var that = this;
  var index = that.index;
  that.index++;
  return function (data) {
    that.counter++;
    that.results[index] = callback ? allback(data) : data;
    if (that.counter >= that.index) {
      that.callback(that.results);
    }
  };
};

var after = new After(function (list) {
  console.log(list);
});
[1, 2, 3, 4, 5, 6, 7].forEach(function (val) {
  setTimeout(after.group(), Math.random() * 100, val);
});

所以原有代码只要稍作改动就可以了：）

function foo (x, callback) {
  var after = new After(callback);
  for (i = x; i > 0; i--) {
    var obj = new RemoteObj();
    obj.rpc_call(x, after.group(function (result) {
      // 把result的结果和x的值做计算
      // ...
      // ...
      return result;
    }));
  }
}

14行有笔误