如何在 javascript 中聚合 2 个 Promises 返回的数据

Question

我在 js 文件中导入了 2 个承诺。 员工、经理 这两个承诺都包含作为 Json 对象数组的数据。 例如

employees = [ {"id": 1, "name": "Andrew", "age": 22}, {"id": 2, "name": "Eric", "age": 34}] 
managers = [ {"id": 1, "name": "Andrew", "department": "logistics"}, {"id": 2, "name": "Eric", "department": "sales"}]

我想根据 id 合并这些数据集并返回单个 Json 对象数组，如下所示-

empManager = [ {"id": 1, "name": "Andrew", "age" : 22, "department": "logistics"}, {"id": 2, "name": "Eric", "age": 34, "department": "sales"}]

我正在尝试使用 Promise 链接，但它不起作用

import {employees, managers} from './model';

export let empManager = function getData() {
    let employees;
    employees().then(emps => {
        employees = emps;
        return managers;
    }).then(mgrs => {
        return employees.map( e=> Object.assign(e, mgrs.find(m => m.id == e.id)))
    })
}

当我试图从 empManager 获取值时，如下所示，它给出了错误。

console.log(empManager())  // error - "mgrs.find is not a function".

我应该如何对 2 个 promise 的结果进行聚合？

Answer 1

您可以先使用Promise.all 解决这两个承诺。

// Mimic async call.
employees = () => new Promise(resolve => resolve([ {"id": 1, "name": "Andrew", "age": 22}, {"id": 2, "name": "Eric", "age": 34}]));
managers = () => new Promise(resolve => resolve([ {"id": 1, "name": "Andrew", "department": "logistics"}, {"id": 2, "name": "Eric", "department": "sales"}]));

// Wrap in async anonymous function to be able to use await.
(async () => {

  // Use Promise.all to wait for both calls
  const [emps, mgrs] = await Promise.all([
    employees(),
    managers()
  ]);

  // Merge epmloyees
  const merged = {};
  emps
    .concat(mgrs)
    .forEach(u => {
      if(!(u.id in merged)) {
        merged[u.id] = {};
      }
      for(const key in u) {
        merged[u.id][key] = u[key];
      }
    })
  ;

  // Convert merged object into array again.
  console.log(Object.values(merged));

})();