异步模块返回promise [对象Promise]

Question

我正在尝试使用instrument variable导出该值。然而，数据以对象承诺的形式返回，而不是对象。如何使用最终结果而不是promise对象来赋值模块变量。

var instruments = { 
    data: async () => {
        return new Promise((resolve, reject) => { 
            /// Respond after retrieving the data 
            resolve({result : "...." }
        );
    }
}

var symbols =   async () => {
    const res = await instruments.data();
    return res;
}

module.exports.instrument  =  symbols().then((data) => {
    console.log('data');
    return data; 
}).catch((e) => {
   console.log('error');
   return {}
}); 

Answer 1

看起来你想要一个singleton缓存。下面是一个基本的实现

cache.js

let data = {}

module.exports = {
  getData: () => {
    return data
  },
  setData: newData => {
    data = newData
    return
  },
}

这里不需要异步。我会将这段代码与检索数据的代码分开。

fetchData.js

const cache = require('./cache')

const fetchData = () => {} // fetch data code here

fetchData().then(data => {
  cache.setData(data)
})

Answer 2

尝尝这个

var instruments = { 
data:  () => {
    return new Promise((resolve, reject) => { 
        /// Respond after retrieving the data 
             resolve({result : "...." }); 

}
}

var symbols =   async () => {
    const res = await instruments.data();
    return res;
}

module.exports.instrument  =  symbols;

然后导入instrument方法进行调用，然后调用

const instrument  = require("./filepath");

instrument().then((data) => {
    console.log('data');

    }).catch((e) => {
   console.log(e);
   }); 

Answer 3

如果你的异步函数instruments.data()被调用，它将await返回Promise。只需在return中添加await即可获得预期结果。

var instruments = { 
    data: async () => {
        return await new Promise((resolve, reject) => { 
             // Respond after retrieving the data 
             resolve({result : "...." }); 
        }
}

或者删除async。和上面的一样。

var instruments = { 
    data: () => {
        return new Promise((resolve, reject) => { 
             // Respond after retrieving the data 
             resolve({result : "...." }); 
        }
}