如何导出承诺结果？ [英] How can I export promise result?

问题描述

很抱歉，如果这个问题很愚蠢。

Sorry if this question is stupid.

此代码可以正常使用。并且我只需要在所有promises成功解析后导出数据变量。

This code works correctly. And I just need to export data variable after all promises successfully resolved.

我不能将此代码用于函数和导出变量。因为在这种情况下，此函数将导出一个空数组。

I cannot put this code to function and export variable. Because in this case, this function will export an empty array.

'use strict'

import urls from './urls'
import getData from './get-data'

getData(urls).then((responses) => {
    const data = []
    const results = responses.map(JSON.parse)

    for (let i = 0, max = results.length; i < max; i++) {
        // some magic and pushing 
    }

    return data
}).catch(error => console.log(error))

推荐答案

您可以轻松地将其分配给导出的变量，但您应该不这样做 - 赋值是异步发生的，并且可以在导入它的模块中读取变量。

You could easily assign it to an exported variable, but you should not do that - the assignment happens asynchronously, and the variable might be read before that in the modules where it is imported.

所以相反，只需导出promise ¹ ！

So instead, just export the promise¹!

// data.js
import urls from './urls'
import getData from './get-data'

export default getData(urls).then(responses =>
    responses.map(JSON.parse).map(magic)
);

// main.js
import dataPromise from './data'

dataPromise.then(data => {
    console.log(data);
    …
}, console.error);

_{1：直到建议顶级 await 出现，您可以在导出前等待该值它。}

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