node.js - 需要一些帮助以更好地理解代码

Question

这是一个有效的代码，因此只需要了解某些部分就会有所帮助。

上传.js::

const util = require("util");
const multer = require("multer");
const GridFsStorage = require("multer-gridfs-storage");
const mongoose = require('mongoose');
const Grid = require('gridfs-stream');

const mongoURI ='mongodb://localhost:27017/file_uploaded_new';
const promise = mongoose.connect(mongoURI, { useNewUrlParser: true });
const conn = mongoose.connection;
**let gfs;
conn.once('open',() => {
  gfs = Grid(conn, mongoose.mongo);
  gfs.collection('uploads');
});**

**var storage = new GridFsStorage({**
    db: promise,
    **options: {useNewUrlParser: true, useUnifiedTopology: true }**,
    file: (req, file) => {
        return new Promise((resolve, reject) => {
            if (file.mimetype === 'application/vnd.openxmlformats- 
   officedocument.wordprocessingml.document') {
                resolve({
                    bucketName: 'words',
                    filename: `${file.originalname}`
                })
            } else {
                reject(Error("File type has been rejected"));
            }
        });    
    }
});

**var uploadFile = multer({storage: storage}).single("file");**

**var uploadFilesMiddleware = util.promisify(uploadFile);
module.exports = uploadFilesMiddleware;**

需要具体了解代码的粗体部分。得到了源代码，但没有解释。所以理解它真的很有帮助。

标签： node.jsexpress