javascript - 无法从 'async' 函数获取返回值 - Javascript

Question

我正在使用 javascript 中的一些异步函数，但我遇到了一个问题，我已经发布了 here但这对每个人来说都是一种不切实际的体验。现在，我做了一个简单的构造函数，里面有相同的成员函数并返回了一个值，但对我来说似乎是同样的问题，我尽力了但我不知道问题是什么，如果你运行这段代码然后你可以检查我想要的是。这是 demo link在 JSfiddle 上，您可以在 console 上看到结果。

这是我的代码

function Test() {
  this.init = async function() {
    var count = 0,
      page_job_details = null;

    async function waitMore() {
      console.log("Wait more loaded - " + (count + 1) + "...");
      let p = new Promise(function(res, rej) {
        setTimeout(async function() {
          if (count === 2) {
            res({
              page_job_details: "khan"
            });
          } else {
            count++;
            waitMore();
          }
        }, 2000);
      });
      var res = await p;
      if (res.page_job_details === '' || res.page_job_details === 'undefined' || res.page_job_details === null) {
        console.log("waiting more...");
        waitMore();
      } else {
        console.log("Response is : " + res.page_job_details);
        return res;
      }
    }
    var khan;
    await waitMore().then(function(r) {
      console.log(r);
      khan = r;
    });
    return khan;
  }
}
new Test().init().then(function(res) {
  console.log(res);
})

When you comment out the conditions within the setTimeout() and simply res({page_job_details:"khan"}); then you'll get the results in the new Test().init().then(function(res){ console.log(res); }). Otherwise not, and that's the main problem.

Answer 1

其中一个问题是您没有从 promise 中返回递归调用的结果。

不只是递归地调用它

waitMore();

您似乎期望递归调用的结果沿着管道返回

res(waitMore());

function Test() {
  this.init = async function() {
    var count = 0,
      page_job_details = null;

    async function waitMore() {
      console.log("Wait more loaded - " + (count + 1) + "...");
      let p = new Promise(function(res, rej) {
        setTimeout(async function() {
          if (count === 2) {
            res({
              page_job_details: "khan"
            });
          } else {
            count++;
            res(waitMore());
          }
        }, 2000);
      });
      var res = await p;
      if (res.page_job_details === '' || res.page_job_details === 'undefined' || res.page_job_details === null) {
        console.log("waiting more...");
        waitMore();
      } else {
        console.log("Response is : " + res.page_job_details);
        return res;
      }
    }
    var khan;
    await waitMore().then(function(r) {
      console.log(r);
      khan = r;
    });
    return khan;
  }
}
new Test().init().then(function(res) {
  console.log(res);
})