返回未定义的异步函数

Posted 2023-02-27

【中文标题】返回未定义的异步函数

【英文标题】：Async Functions returning undefined

【发布时间】：2016-05-07 23:47:10

【问题描述】：

我正在从 GraphQL 服务器获取数据，我正在尝试通过 babel 实现 ES7 Async 函数。我目前在控制台中收到undefined，但我不确定自己做错了什么。

import fetch from 'isomorphic-fetch';
/**
 * [transport creates call to server with isomorphic-fetch]
 * @param  [String] path        [url to hit with request]
 * @param  [Object] query       [The GraphQL query/mutation]
 * @param  [Object] queryParams =  [Params to pass into query]
 * @return [Promise]            [Promise containing payload]
 */
 //function that returns a promise
 export function transport (path, query, queryParams = ) 
     return new Promise ((resolve, reject) => 
       return fetch(path, 
             method: 'POST',
             headers: 
                 'Accept': 'application/json',
                 'content-type': 'application/json'
             ,
             body: JSON.stringify(
                 query,
                 queryParams
             )
         )
         .then(res => res.json())
         .then(response => 
           if(response.errors) 
             return error(response.errors);
           
           return resolve(response.data);
         )
         .catch(error);
     );
 

import  transport  from './utils/transport.js';

/**
 * [reachGraphQL Makes queres or mutations against GraphQL]
 * @param  [String] path        [path to the GraphQL server]
 * @param  [Object] query       [The query that GraphQL will use to fetch your data]
 * @param  [object] queryParams =   [Should contain object with different query params]
 * @return [Object]             [Data that was queried or mutated]
 */
//Heres Where I'm awaiting a promise from the transport function
export function reachGraphQL (path, query, queryParams = ) 
  async () => 
    try
      let response = await transport(path, query, queryParams);
      return response;
     catch (error) 
      console.log(error)
    
  

【问题讨论】：

你的 promise 实现了 resolve，但不会在错误时调用 reject。你的代码会吞下异常吗？

不完全确定，我认为这是我在reachGraphQL() 上使用异步的方式

“错误”在哪里定义？

对不起，我的意思是在顶部模块中

看起来如果 response.errors 是事实，你的承诺会吞下一个异常，说“错误未定义”

【参考方案1】：

您的 reachGraphQL 只是定义了一个 async 箭头函数，但没有对其做任何事情。它没有return 任何东西。相反，它应该是async 本身：

export async function reachGraphQL (path, query, queryParams = ) 
    try 
        return await transport(path, query, queryParams);
     catch (error) 
        console.log(error)
    

【讨论】：

它们会导致以下情况：bundle.js:53 Promise _d: Object bundle.js:125 ReferenceError: error is not defined(...) but does not respond with the retrieved information.跨度>

如 cmets 所述，.catch(error); 是个问题。