从承诺中获取数据 [英] Get data from a Promise

问题描述

我正在使用 Tabletop.js 从我的Google电子表格中获取数据。在函数中，我调用了Promise。唯一的问题是我无法从函数中获取数据。

I'm working with Tabletop.js to get data from my Google Spreadsheet. In the function, I've invoked a Promise. The only problem is I can't get the data(which is an Array) out of the function.

我有以下代码：

function getData() {

  return new Promise((resolve) => {
    Tabletop.init({key: publicSpreadsheetUrl, callback: showInfo, simpleSheet: true})
    resolve('Done');
  })
}

let arrayWithData = [];

function showInfo (data, tabletop) {
  console.log('showInfo active');
  arrayWithData.push(...data);
  return new Promise(resolve => {
    console.log(arrayWithData, 'data is here')
    resolve(arrayWithData) // This doesn't work yet
  })
}
 showInfo().then(data => {
   console.log(data, 'data from the Promise')
 }) // This doesn't work

我想稍后在React块中使用Array

I want to use the Array later on in React blocks

编辑
有了Keith的代码段，我的代码可以正常工作了。还从拒绝处理程序Web / JavaScript /参考/ Global_Objects / Promise / reject＃Examples rel = nofollow noreferrer> MDN网站。

Edit With the snippet of Keith, I've got my code working & also added a reject handler(inside my Promise of getData() ) from the MDN site.

Promise.reject(new Error('fail')).then(function() {
  // not called
}, function(error) {
   console.log(error); // Stacktrace
});

唯一的是，我不理解从<$ c $中得到的错误c> Promise.reject 。它返回以下错误：

The only thing is, that I don't understand the error I get from my Promise.reject. It returns the following error:

Error: fail
at eval (eval at hmrApply (base.eaab6c8c.js:297), <anonymous>:37:20)
at new Promise (<anonymous>)
at getData (eval at hmrApply (base.eaab6c8c.js:297), <anonymous>:30:10)
at Object.eval (eval at hmrApply (base.eaab6c8c.js:297), <anonymous>:63:1)
at newRequire (script.726c79f3.js:48)
at hmrAccept (base.eaab6c8c.js:328)
at base.eaab6c8c.js:214
at Array.forEach (<anonymous>)
at WebSocket.ws.onmessage (base.eaab6c8c.js:212)

推荐答案

您

首先，您有 showInfo（）。然后，我是我很确定你打算这么做-> getData（）。then（

Firstly, you have showInfo().then, I'm pretty sure you meant to do -> getData().then(

下一个问题是您的getData函数，就像@ChrisG所说的那样，您刚刚在这里立即兑现诺言，下面更可能是您的意思。

Your next problem is your getData function,. like @ChrisG said your just resolving a promise instantly here, below is more likely what you meant to do.

function getData() {
  return new Promise((resolve) => {
    Tabletop.init({key: publicSpreadsheetUrl, 
      callback: function (data, tabletop) { resolve(showInfo(data, tabletop)); },
      simpleSheet: true})
  })
}

最后，您的showInfo没有执行任何操作异步，因此可以简化为->

Lastly your showInfo is not doing anything async so it can be simplified to ->

function showInfo (data, tabletop) {
  console.log('showInfo active');
  arrayWithData.push(...data);
  console.log(arrayWithData, 'data is here')
  return arrayWithData;
}

最后一件事，这里没有错误检查，通常回调有某种方式通知您有错误情况，那么您还可以添加拒绝处理程序。

One last thing, there is no error checking here, normally callbacks have some way to inform you of an error condition, then you could also add the reject handler.

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