javascript - Promise 无法通过异步得到解决

Question

我正在使用 igmur api 上传图像。我使用 Promises、async-await 在 Node.js 中编写了一个应用程序。 (请注意，我对这些概念还很陌生)。

我的代码似乎确实有效。它将图像上传到 igmur。但问题是， promise 并没有得到解决。请引用下面的代码。

router.post('/images/upload', async (req, res) => {
    /* we would receive a request of file paths as array */
    let filePaths = req.body.urls;

    let multipleUpload = new Promise(async (resolve, reject) => {
            let upload_len = filePaths.length,
                upload_res = new Array();

            for (let i = 0; i <= upload_len + 1; i++) {
                let filePath = filePaths[i];
                await imgur.upload(filePath, (error, result) => {
                    console.log(" A -> ");
                    if (upload_res.length === upload_len) {
                        console.log("******");
                        /* resolve promise after upload is complete */
                        resolve(upload_res)
                    } else if (result) {
                        /*push public_ids in an array */
                        console.log("OK")
                        upload_res.push(result.public_id);
                    } else if (error) {
                        console.log(error)
                        reject(error)
                    }

                })

            }
        })
        .then((result) => console.log(result))
        .catch((error) => error)

    let upload = await multipleUpload;
    res.json({
        'response': upload
    })
})

我关注了这个tutorial ，它做了类似的事情。

Answer 1

我至少看到两个问题:

• 在不需要时将异步与 Promise 混合使用
• 我怀疑 imgur.upload 没有返回 Promise，因为它接受回调函数。

我认为这应该解决它:

router.post('/images/upload', async (req, res) => {
  let filePaths = req.body.urls
  let upload_len = filePaths.length
  let multipleUpload = filePaths.map(filePath => {
    return new Promise((resolve, reject) => {
      imgur.upload(filePath, (err, result) => {
        if (err) {
          reject(err)
        } else {
          resolve(result.public_id)
        }
      })
    })
  })

  let upload = await Promise.all(multipleUpload)

  res.json({
    response: upload,
  })
})