Javascript异步在循环内获取请求 [英] Javascript async get request inside loop

问题描述

我有一个看起来像这样的对象数组:

I have an array of objects that looks like this:

[ { firstName: 'Mike', lastName: 'Jones' },
  { firstName: 'Joe', lastName: 'Smith' },
  { firstName: 'Bob', lastName: 'Johnson' } ]

我需要将该数组传递给一个函数，该函数将向每个对象添加一个"middleName"字段，并为MiddleName赋一个值.该函数通过在Node中发出异步http.get请求来获取中间名.问题就在这里.无论如何尝试，我都无法完成这项工作.

I need to pass that array to a function that's going to add a "middleName" field to each object, and a value for middleName. The function gets the middle name by making an asynchronous http.get request in Node. And therein lies the problem. I can't make this work no matter how I try.

以前有人建议过这样的循环:

Previously someone suggested a loop like this:

array.forEach(function (obj) {
        GetMiddleName(obj, function (person) {
            obj.MiddleName = person;
        });
    });

但是，由于在GetMiddleName函数中调用get的异步特性，因此无法正常工作.谁能给我看一个简短，简单的函数来满足我的需求?

But that doesn't work due to the async nature of the get being called in the GetMiddleName function. Can anyone show me a short, simple function that will do what I need?

推荐答案

制作一个Promises数组，在该数组上调用 Promise.all ，然后在每个数组中插入中间名:

Make an array of Promises, call Promise.all on that array, and then insert the middle name to each:

const getMiddleNameProm = obj => new Promise((resolve) => {
  GetMiddleName(obj, resolve);
});
Promise.all(arr.map(getMiddleNameProm))
  .then((middleNames) => {
    for (let i = 0; i < middleNames.length; i++) {
      arr[i].MiddleName = middleNames[i];
    }
    // do stuff with populated arr here
  });
});

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