Javascript 环内承诺链

cleanupInstance

也是一个承诺链。然而，目前我的for循环在整个承诺链完成之前进入下一个迭代。有没有一种方法也能保证循环？我正在使用蓝鸟图书馆（nodejs）进行承诺。

您可以使用：

---

为什么不使用

Promise.each

或

Promise.all

？这将更加容易理解和灵活

请检查下面的例子

var Promise = require('bluebird');
...
Promise.each(listofInstances, function(instance) {
  return cleanupInstance(instance).then(function() {
    console.log('Done', instance);
  });
}).then(function() {
  console.log('Done with all instances');
});

或者您可能有循环中的循环。如果你有一个数组的数组，那就举个例子

var Promise = require('bluebird');
var someArray = ['foo', 'bar', 'baz', 'qux'];

Promise.all(someArray.map(function(singleArrayElement){
  //do something and return
  return doSomethingWithElement(singleArrayElement);
})).then(function(results){
  //do something with results
});

Promise.each(someArray, function(singleArrayElement){
  //do something and return
  return doSomethingWithElement(singleArrayElement);
}).then(function(results){
  //do something with results
});

---

请解释当all循环中有多个承诺链时，代码将是什么。
例如：

var Promise = require('bluebird');
var arrayOfArrays = [['foo', 'bar', 'baz', 'qux'],['foo', 'bar', 'baz', 'qux']];

function firstLoopPromise(singleArray){
  return Promise.all(singleArray.map(function(signleArrayElement){
    //do something and return
    return doSomethingWithElement(signleArrayElement);
  }));
}


Promise.all(arrayOfArrays.map(function(singleArray){
  //do something and return
  return firstLoopPromise(singleArray);
})).then(function(results){
  //do something with results
});

var Promise = require('bluebird');
var arrayOfArrays = [['foo', 'bar', 'baz', 'qux'],['foo', 'bar', 'baz', 'qux']];

function firstLoopPromise(singleArray){
  return Promise.all(singleArray.map(function(signleArrayElement){
    //do something and return
    return doSomethingWithElement(signleArrayElement);
  }));
}


Promise.all(arrayOfArrays.map(function(singleArray){
  //do something and return
  return firstLoopPromise(singleArray);
})).then(function(results){
  //do something with results
});

Promise.all(someArray.map(function(singleArrayElement){
    //do something and return
    return doSomethingWithElement(singleArrayElement)
    .then(function(result){
    return doSomethingWithElement(result)
})
.then(function(result){
    return doSomethingWithElement(result)
})
})).then(function(results){
    //do something with results
});