使用延迟到多个ajax调用的链循环 [英] Using deferred to chain loops with multiple ajax calls

问题描述

有很多问题已经对此有了答案，但到目前为止所有这些都没有用到这种设置。

There are multiple questions that already have an answer about this, but all aren't working so far it this kind of setup.

function login(u,p) {
   console.log(1);
   return $.post(url, {u,p});
}

function out() {
   console.log(3);
   //a function that does not return deferred
   // clear cookies
}

function doSomething() {
  console.log(2);
  // a function that returns a deferred
  return $.post(...);
}
var data = [{u: 'au', p: 'ap'}, {u: 'bu', p: 'bp'}]

$.each(data, function(k,v){
  login(v.u, v.p).then(doSomething).then(out);
});

我原以为它的序列如下：

I was expecting it's sequence to be like:

1
2
3
1
2
3

但是我得到了

1
2
1
3
2
3

为什么是这样的，即使我等待承诺使用解决，然后

Why is it like that, even though I am waiting for the promise to be resolve using then

推荐答案

这个想法是创建一个像@Popnoodles所提到的递归函数。

The idea is to create a recursive function like @Popnoodles have mentioned.

例如

function a() {
  return $.post();
}

function b() {
  return $.post();
}

function c() {
   console.log('no promise.');
}

// and the recursive main function

function main() {
   if(counter < data.length){
      $.when(a().then(b).then(c)).done(function(){
        counter++;
        main();
      });
   }
}

main();

以下是它的工作原理，打开控制台，看看它是如何按顺序记录功能的。

Here is how it works, open the console to see how it logs the function in sequence.

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