NodeJS - 使用 Array.protoype.map() 从异步函数返回单个状态代码以将多个文件保存在数据库中的不同位置

Question

I am a little stumped on how to handle this the best way possible. I've decided to rewrite this controller, and I need to (at least I think) make use of promise.all() here.

Premise:

In this application, the Admin user must be able to bulk upload a bunch of .pdf's at once that are for multiple users. The .pdf's adhere to a specific naming convention that my backend upload controller by using a regEx , pulls out a first and last name. These .pdf's are auto-generated in a program, that always names them exactly the same, so there is no human error in misspelling names.

Each call to the database and an AWS S3 Bucket is made within an Array.prototype.map() a function that is looping through and uploading a file to an S3 bucket, and then it takes the Key name of the file returned from s3.upload() and saves that Key to a user model in Mongo DB as a reference to their file(s) within the S3 Bucket.

Example Code:

This is what I currently have (that does work somewhat). This is the block of code responsible for what I described above. employeeFiles is created further up in the controller and contains an array of objects that each have a file and id property. The file name destructuring and user matching happen further up in the controller as well, and the employeeFiles array is a result of that. The id property contains the mongo _id of the employee, and the file property contains the file to be saved. This all works perfectly, and I don't think that code is needed for context here. fileType is a variable available within the scope of the controller:

const employeeFileUploadToDb = () => {

  employeeFiles.map((employee, i) => {
    const { file, id } = employee;
    const params = {
      Bucket: S3_BUCKET_NAME,
      Body: file.buffer,
      Key: `${filetype}/${file.originalname}`
    };
    s3.upload(params, (err, data) => {
      if (err) {
        next(err);
      }

      if (data) {
        //Save reference to Employee model
        let dataObj = {
          key: data.key,
          fileName: file.originalname,
          date: Date.now()
        };

        Employee.findOneAndUpdate(
          { _id: id },
          { $push: { [`${filetype}`]: dataObj } }
        )
          .then(resp => res.send(200))
          .catch(err => next(err));
      }
    });
  });
};

I am making use of next() to handle any errors within the s3.upload() and findOneAndUpdate() functions (I do realize findOneAndUpdate() is deprecated) moving forward. My idea here is that if there is an error with one of the functions, next() will send it to my error handler middleware and keep going, versus ending the process and halting all of it.

Inside of every iteration of s3.upload() , I make a call to my database so that I can save the reference to the file uploaded to the S3 Bucket . Inside of a then() method of Employee.findOneAndUpdate() , I return a (200) response to let my client know everything has been uploaded to S3 and saved in my DB. So on each iteration of this map() function, I am returning a 200. If I have 10 files, I am returning 200 10 times.

I feel that I can convert this into an async function, and make use of a promise.all() to return a single status code upon completion. Returning that many status codes seem a bit crazy to me. But I am not too sure how to approach this while using a map() function to loop and make an async call on every iteration.

Hope this makes sense, and thank you in advance for looking at this!

Answer 1

I would split it up into a 2-step process. Upload in bulk and then save to mongo if it all worked out.

const employeeFileUploadToDb = () => {

  const uploadFiles = files => files.map((employee, i) => new Promise((resolve, reject) => {
    //...
    s3.upload(params, (err, data) => {
      if (err) {
        return reject(err);
      }
      resolve(data);
     })
    });
  });


  Promise.all(uploadData(employeeFiles)).then((err, data) => {
     // Handle saving to mongo
  })
};