如何从Node.js中的两个嵌套回调函数返回数据

Question

I need to return the s3Url array. How to return s3Url array and suggest me is there any other best way to upload the data to s3 and return the s3Url

exports.s3Media = fileName => {
          let s3Url = [];
          (async () => {
            for (let i = 0; i < 6; i++) {
              await fs.readFile(`${fileName[i]}`, (err, data) => {
                if (err) throw err;
                const params = {
                  Bucket: `research-1`,
                  Key: fileName[i],
                  Body: JSON.stringify(data, null, 2)
                };
                s3.upload(params, function(s3Err, data) {
                  if (s3Err) throw s3Err;
                  s3Url.push(data.location);
                });
              });
            }
            return s3Url;
          })();
        };

Answer 1

There are more things wrong with your code. You are not using Async/Await in the right way.

1. Take a look at Async/Await: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/async_function

2. If you want to go with the Async/Await you have to promisify readFile(), have a look at this answer here: reading file with ES6 promises

3. Why are you using a self invoking fn inside the s3Media, maybe you can make the whole fn async (this will return a promise)

4. The return is not in the right position

Dig a little on your own and you will get there. I hope it helps.