获得一系列未决承诺 [英] Getting an array of pending promises

问题描述

var arr = [1,2 ,3, 4, 5, 6, 67, 8, 10];

function f1 () {

   return arr.map(function (member) {

       console.log(member);
        return Promise.resolve(member + 2).then((result) => {return result + 2}).then
        (value => {return value + 1});

    });



}

console.log(f1());

输出数组为 Promise {< pending>每个索引都有。有什么问题？我认为返回值+ 1 最终解决了承诺，为什么我要等待？

The output is an array of Promise { <pending> } at every single index. What is the issue? I thought the return value + 1 at the end resolved the promises, so why am I getting pending?

推荐答案

代码没有问题，预计会发生什么。

There is no issue with the code, what happens is expected.

我认为返回值+ 1 最后解决了承诺

不，这不是 return 本身，它是然后功能，它将使用回调函数的返回值来解析promise。

No, it's not the return itself, it's the then functionality that will resolve the promise with the return value of the callback function.

不，它还没有解决承诺，将解决未来的承诺 。 然后回调总是异步调用。

And no, it didn't resolve the promise yet, it will resolve the promises in the future. then callbacks are always called asynchronously.

为什么我要等待？

so why am I getting pending?

因为当你记录它们时它们仍处于未决状态;之后会立即解决。

Because the are still pending when you log them; they will get resolved immediately afterwards.

如果要记录结果数组，请使用

If you want to log an array of the results, use

Promise.all(f1()).then(console.log);

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