node.js - 并发(迭代)调用 Promise.all() 的函数时出现问题

Question

这个例子是一个简化，但希望能说明我的问题。我怀疑我在这里遗漏了一些明显的回复:关闭。

问题是，从下面的聚合函数返回的结果包括 personParams 的最终集，即那些由 forEach 最终迭代产生的结果，而不是调用该函数的 personParams 集.

let promiseArray = [];  // top level array of promises

let globalParams = { date: "2018-05-20" };
let people = [
              {name: "Tom",
               location: "Philadelphia"},
              {name: "Bob",
               location: "Austin"},
              {name: "John",
               location: "Philadelphia"}
             ];

people.forEach( person => {

    // Create indivdiualized parameter set
    let personParams = globalParams;
    personParams.name = person.name;
    personParams.location = person.location;

    // Push promise to array
    promiseArray.push(assembleResults(personParams));

});

Promise.all(promiseArray).then( results => {
    console.log("Final Output:", results);  
})

// individual data aggregation function
function assembleResults(iterationParams) {

    let promise1 = Promise.resolve({data: "Type A data about " + iterationParams.name});
    let promise2 = Promise.resolve({data: "Type B data about " + iterationParams.name});
    let promise3 = Promise.resolve({data: "Type C data about " + iterationParams.name});

    return Promise.all([promise1, promise2, promise3, iterationParams])
}

更新了可执行文件 Fiddle @ JSFiddle https://jsfiddle.net/shaunhurley/9r5k6j0c/

我的期望是 assembleResults() 的每次迭代都会返回一个如下所示的数组:

[{data: "Type A data about <person's name>"},
 {data: "Type B data about <person's name>"},
 {data: "Type C data about <person's name>"},
 {date: "2018-05-20", name: "<person's name>", location: "<location>"}]

其中每个数组的名称分别设置为“Tom”、“Bob”和“John”。最终输出将是下面的一个或多个数组。

[{data: "Type A data about Tom"},
 {data: "Type B data about Tom"},
 {data: "Type C data about Tom"},
 {date: "2018-05-20", name: "Tom", location: "Philadelphia"}]

[{data: "Type A data about Bob"},
 {data: "Type B data about Bob"},
 {data: "Type C data about Bob"},
 {date: "2018-05-20", name: "Bob", location: "Austin"}]

[{data: "Type A data about John"},
 {data: "Type B data about John"},
 {data: "Type C data about John"},
 {date: "2018-05-20", name: "John", location: "Philadelphia"}]

实际结果是，虽然返回了正确的数据集，但每个数组中包含的参数集显示了生成的最后/最终参数集，即名称==“约翰”和位置==“费城”

[{data: "Type A data about Tom"},
 {data: "Type B data about Tom"},
 {data: "Type C data about Tom"},
 {date: "2018-05-20", name: "John", location: "Philadelphia"}]

[{data: "Type A data about Bob"},
 {data: "Type B data about Bob"},
 {data: "Type C data about Bob"},
 {date: "2018-05-20", name: "John", location: "Philadelphia"}]

[{data: "Type A data about John"},
 {data: "Type B data about John"},
 {data: "Type C data about John"},
 {date: "2018-05-20", name: "John", location: "Philadelphia"}]

任何想法将不胜感激......

谢谢!

肖恩

Answer 1

people.forEach(person => {
  let personParams = globalParams;
  personParams.name = person.name;

  promiseArray.push(assembleResults(personParams));
});

在上面的代码块中，您调用了person.name，我可以看到每个人都是一个字符串。所以你得到的是未定义而不是人名。我认为应该是 personParams.name = person。

和 assembleResults() 函数的 getResultsA getResultsB 和 getResultsC 不应返回任何数据，除非您有一些数据名为未定义的人。

我猜这是您发布的虚拟代码。发布真实的代码将有助于我更准确地回答。

修改

下面的代码可以完成你的工作:

people.forEach((person) => {
  // Create indivdiualized parameter set
  const personParams = {
    date: globalParams.date,
    name: person.name,
    location: person.location
  }
  // Push promise to array
  promiseArray.push(assembleResults(personParams));
});

解释它是如何工作的会花费太长时间，而且我想你已经知道它为什么会这样了。请google“JavaScript 对象创建”。