多个异步回调 - 使用数组来完成时触发功能 [英] Multiple Asynchronous Callbacks - Using an array to fire function when complete

问题描述

我使用Node.js的，使多个异步调用我需要时，他们处理数据全部完成。我被他们筑巢，但是这真的是低效的，因为人们不会开始，直到previous完成。我想出了这一点，只是想知道如果有什么公然错的：

 变种F =功能（）{}，
    actualCallback =函数（）{/ *做真正的东西* /}，
    回调= [F，F，F，F，actualCallback]aync（函数（）{
    callbacks.shift（）（）;
}）;
aync（函数（）{
    callbacks.shift（）（）;
}）;
aync（函数（）{
    callbacks.shift（）（）;
}）;
aync（函数（）{
    callbacks.shift（）（）;
}）;
aync（函数（）{
    callbacks.shift（）（）;
}）;
 

解决方案

你能不能定义通过数组的工作方式的功能？

 函数asyncSequence（回调）{
  功能doAsync（）{
    异步（函数（）{
      如果回报（callbacks.length！）;
      回调[0]（）;
      回调= callbacks.slice（1）;
      的setTimeout（doAsync，0）;
    }）;
  }
  doAsync（）;
}
 

然后调用与您的回调函数数组。

现在，如果你想同时推出所有的异步回调，那么我没有看到摆在首位的问题;刚开始他们是必要的。如果你需要做一个排序的加盟在所有这些的结尾，然而，那么你就必须跟踪的常规状态：

 函数asyncSequenceConcurrent（回调，whenFinished）{
  无功不全= callbacks.length;
  对于（VAR I = 0; I＆LT; callbacks.length ++我）{
    异步（（功能（我）{
      返回功能（）{
        回调[I]（）;
        incomplete--;
        如果（！不完全统计）{
          whenFinished（）;
        }
      };
    }）（一世））;
  }
}
 

I'm using Node.js and making multiple Asynchronous calls that I need to handle data with when they all finish. I was nesting them, but this was really inefficient as one wouldn't start until the previous finished. I came up with this, and just wondering if there's anything blatantly wrong with it:

var f = function(){},
    actualCallback = function() { /* Do real stuff */ },
    callbacks = [f, f, f, f, actualCallback];

aync(function() {
    callbacks.shift()();
});
aync(function() {
    callbacks.shift()();
});
aync(function() {
    callbacks.shift()();
});
aync(function() {
    callbacks.shift()();
});
aync(function() {
    callbacks.shift()();
});

解决方案

Can't you define a function that works its way through the array?

function asyncSequence(callbacks) {
  function doAsync() {
    async(function() {
      if (!callbacks.length) return;
      callbacks[0]();
      callbacks = callbacks.slice(1);
      setTimeout(doAsync, 0);
    });
  }
  doAsync();
}

Then you call that with your array of callback functions.

Now, if you want to launch all the asynchronous callbacks concurrently, then I don't see the problem in the first place; just start them as necessary. If you need to do a sort of "join" at the end of all of them, however, then you'd have to keep track of the general status:

function asyncSequenceConcurrent(callbacks, whenFinished) {
  var incomplete = callbacks.length;
  for (var i = 0; i < callbacks.length; ++i) {
    async((function(i) {
      return function() {
        callbacks[i]();
        incomplete--;
        if (!incomplete) {
          whenFinished();
        }
      };
    })(i));
  }
}

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