JavaScript-可以从功能带有承诺的函数返回值

发布于 2025-02-10 10:05:03 字数 567 浏览 1 评论 0原文

我正在学习JavaScript中的Promise，但我不明白为什么我的功能不返回正确的值。

这是我的功能：

function promise() {
  let p = new Promise((resolve, reject) => {
    return resolve(["a", "random", "array"]);
  });

  p.then((response) => {
    return response;
  }).catch((error) => {
    return error;
  });
}

console.log(promise());

如果我运行代码，我会得到不确定的。

我认为问题在于console.log是在返回的值之前执行的。

有人可以帮助我解决这个问题并解释这个问题吗？ :)

感谢您的每一个答案。

原文

I am learning promise in JavaScript but I don't understand why my function doesn't return the right value.

This is my function:

function promise() {
  let p = new Promise((resolve, reject) => {
    return resolve(["a", "random", "array"]);
  });

  p.then((response) => {
    return response;
  }).catch((error) => {
    return error;
  });
}

console.log(promise());

If I run the code I get undefined.

I think the problem is that the console.log is executed before the value of the .then is returned.

Can somebody please help me to solve this problem and maybe explain the problem? :)

Thanks for every answer.

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迷迭香的记忆 2025-02-17 10:05:03

两件事：

您必须返回 Promise P从Promise> Promise函数中。
您必须等待函数返回的承诺的结果，然后才能访问其满足价值：

function promise() {
  let p = new Promise((resolve, reject) => {
    return resolve(["a", "random", "array"]);
  });

  p.then((response) => {
    return response;
  }).catch((error) => {
    return error;
  });
  
  // 1. Return the promise from the function:
  return p;
}

// 2. Await the result before using it:
promise().then((result) => {
  console.log(result);
});

您说您正在学习有关承诺的知识。异步/等待使所有这一切变得更加容易：

<script type="module">
// Top level await is available in ES modules

async function promise () {
  try {
    return ["a", "random", "array"];
  }
  catch (exception) {
    return exception;
  }
}

const result = await promise();
console.log(result);

</script>

Two things:

You must return the promise p from within the promise function.
You must await the result of the promise returned by the function before you can access its fulfilled value:

function promise() {
  let p = new Promise((resolve, reject) => {
    return resolve(["a", "random", "array"]);
  });

  p.then((response) => {
    return response;
  }).catch((error) => {
    return error;
  });
  
  // 1. Return the promise from the function:
  return p;
}

// 2. Await the result before using it:
promise().then((result) => {
  console.log(result);
});

You said you're learning about promises. Async/await makes all of this much easier:

<script type="module">
// Top level await is available in ES modules

async function promise () {
  try {
    return ["a", "random", "array"];
  }
  catch (exception) {
    return exception;
  }
}

const result = await promise();
console.log(result);

</script>

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