异步函数返回 [object Promise] [英] Async function returns [object Promise]

问题描述

我试图返回一个异步函数，但我要么得到 promise: <{ PENDING } > 或 [object Promise] 而不是 [object Object]

I'm trying to return an async function but I either get promise: < { PENDING } > or [object Promise] instead of [object Object]

我尝试使用 Promise.resolve(value), Promise.resolve().then(return value), return new Promise 返回值((resolve, reject) => {resolve(value)}

从顶层到底层，我的代码如下:

from top-level to bottom my code looks like:

//Top-Level
const getNext = require('getNext');
const next = getNext({
  page,
  value,
  name,
  id,
});


//getNext
const controllerMap = {
  intro: introController
};
async function getNext({ page, value, name, id}) {
  const controller = controllerMap[name];
  return await controller({
    page,
    value,
    name,
    id
  });
}

// Controller
async function introController({ page, value, id }) {
  switch(page)
    case 10:
      // Do something async ie:
      await db.query
    default: return intro[page]
};

如果我从函数中去掉 async 和 await 并从 controller<中提取我的低级 db.query/code> case 到它自己的 async function 我只是得到 promise: <{ PENDING } > 所以我认为这是因为顶级函数没有等待它解决.但是，当我使这些函数异步时，它们会返回对我的静态数据的承诺.我无法理解这些嵌套的 Promise/异步函数.

If I take off async and await from the functions and extract my low-level db.query from the controller case into it's own async function I just get promise: < { PENDING } > so I'm thinking it's because the top level functions aren't waiting for it to resolve. However, when I make those functions async they return promises for my static data. I'm having trouble wrapping my head around these nested promises/async functions.

推荐答案

您不能使异步代码同步.

You cannot make asynchronous code synchronous.

await 关键字让您可以编写看起来是同步的代码，但实际上是异步的.

The await keyword lets you write code that looks synchronous, but is really asynchronous.

您只能在 async 的函数中使用 await.

You can only use await inside a function which is async.

为了使 await 工作，所有 async 函数返回承诺.这些承诺解析为函数的返回值.

To make await work, all async functions return promises. Those promises resolve to be the return value of the function.

简而言之:您具有正常和预期的行为，并且您无法阻止 async 函数返回承诺.

In short: You have the normal and expected behaviour, and you can't prevent an async function from returning a promise.

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