一切承诺解决后退货

问题描述

下面有一个代码示例，我希望在所有承诺都解决之后，从 main函数返回baz变量。

Having a code sample below, I'd like to get baz variable returned from 'main' function after all promises resolved.

exports.foo = function(bar) {

    var baz;

    // some kind of promises are here forming array of promises p
    // some of promises may change the baz variable

    Promise.all(p).then(() => {
      // returning expression for main function is here
      // return baz here // does not work
    });

    // return baz //cannot be done because it would be earlier than all the async promises are resolved
}

推荐答案

在主要返回值之后承诺解决，因此返回一个baz的承诺：

Promises resolve after main returns, so return a promise of baz instead:

exports.foo = function(bar) {
  var baz;
  return Promise.all(p).then(() => baz);
}

exports.foo(3).then(baz => console.log(baz)).catch(e => console.error(e));

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