Return 在所有 promises 解决之后

Question

下面有一个代码示例，我想在所有承诺解决后从 'main' 函数返回 baz 变量。

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
}

Answer 1

Promise 在 main returns 之后解决 ，因此 return 改为 baz 的 promise：

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));