简体   繁体   中英

Promisifying my https.get() function is returning Promise { <pending> }

I'm trying to promisify a function that uses https.get() to get data from an API, so that I can use async await. Here is the example below, it retrieves the data however if I do anything to access the object, such as theData[0] shown below, it will only return Promise { <pending> }

Why am I not able to get asynchronous operation I'm trying for below? Or is there a better way to do this? Basically I'm just trying to make an asynchronous operation with async await, and I need to use https (not fetch, axios, etc).


const myRequest = ((url) => {
  return new Promise((resolve, reject) => {
    https.get(url, res => {
      let data = [];
      res.on('data', chunk => {
        data.push(chunk);
      });
      res.on('end', () => {
         resolve(JSON.parse(data));
      });
      }).on('error', err => {
        console.log('Error: ', err.message);
      });
  });
});


async function getApi() {
  // write your code here
  let url = [url redacted]

  await myRequest(url)
    .then(data => {
      console.log(data[0])
    })
    .catch(err => {
      console.log(err)
    });
}


Edit: refactored my helper function with the error handler:

 }).on('error', err => {
        reject(err)
      });

However the promise is still not delivering properly. If I do a simple console.log of the data

async function getApi() {
  let url = [url redacted]
  const data = await myRequest(url);
  console.log(data)
}

It will return Promise { <pending> } and then the JSON:

Promise { <pending> }
{
  page: 1,
  per_page: 500,
  total: 1,
  total_pages: 1,
  data: [
    {
      date: '5-January-2000',
      open: 5265.09,
      high: 5464.35,
      low: 5184.48,
      close: 5357
    }
  ]
}

I can access that object in the console.log, however, if i try to access anything in this object, it just returns Promise { <pending> } . Such as :

async function getApi() {
  let url = [url redacted];
  const data = await myRequest(url)
  const {high, open} = data.data[0];
  return `High: ${high} \n Open: ${open}`
}

First, you need to handle reject as well, or an error will cause a hang. Add reject(err) to your error handler to correctly bubble up the error.

Once you're sure the issue isn't an error, the await usage needs work. await is a tool that takes a promise, and then waits until it resolves to execute synchronously. If you then an awaited promise, you're not getting anything out of your await.

Rewrite the getApi function as:

async function getApi() {
  let url = [url redacted]
  const data = await myRequest(url);
  console.log(data);
}

That will get and log the data, and if the promise is properly rejected, it will bubble that up as an exception.

The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.

 
粤ICP备18138465号  © 2020-2024 STACKOOM.COM