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下面有一个代码示例，我想在所有 promise 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
}