节点在异步功能完成之前退出 [英] Node exits before async function completes

问题描述

我有一个返回诺言的函数，并且我试图从异步函数中等待它.问题是程序立即完成，而不是等待诺言.

I have a function that returns a promise, and I am trying to await on it from within an async function. The problem is that the program completes immediately, instead of awaiting the promise.

async-test.js:

async-test.js:

function doItSlow() {
    const deferred = new Promise();

    setTimeout( () => {
        console.log( "resolving" );
        deferred.resolve();
    }, 1000 );

    return deferred;
}

async function waitForIt( done ) {

    console.log( "awaiting" );
    await doItSlow();
    console.log( "awaited" );
    done();
}

waitForIt(() => {
    console.log( "completed test" );
});

console.log( "passed by the test" );

构建并运行:

babel --stage 0 --optional runtime async-test.js > at.js && node at.js`

结果:

awaiting
passed by the test

立即解决而不是等待一秒钟是没有效果的:

Resolving immediately instead of waiting one second has no effect:

function doItSlow() {
    const deferred = new Promise();

    console.log( "resolving" );
    deferred.resolve();

    return deferred;
}

有趣的是，即使现在是同步的，"resolving"也不会被打印:

Interestingly, "resolving" is never printed, even though it is now synchronous:

awaiting
passed by the test

我会怀疑编译器有问题，但是我检查了Babel的输出，并且肯定地，它确实编译了同步版本.

I would suspect a compiler problem, but I checked Babel's output and sure enough, it did compile the synchronous version.

我以为我可以等待异步函数中的诺言.这里有我想念的东西吗?

I thought I could just await on a promise from within an async function. Is there something I am missing here?

推荐答案

您没有正确使用Promise(假设它符合标准).它没有resolve方法.您应该改为传递一个函数:

You are not using Promise right (assuming it's standard compliant). It doesn't have resolve method. You should pass a function instead:

function doItSlow() {
  return new Promise(resolve => {
    setTimeout( () => {
      console.log( "resolving" );
      resolve();
    }, 1000 );
   }); 
 }

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