https://grokonez.com/node-js/multer-build-restapi-to-upload-a-multipartfile-to-nodejs-express

Multer - Build RestAPI to upload a MultipartFile to NodeJS/Express

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In the tutorial, we show how to use Multer middleware for building a RestAPI to upload MultipartFile to NodeJS/Express web-application.

Related posts:

• NodeJs/Express RestAPIs – POST/GET/PUT/DELETE requests

Multer - Upload MultipartFile

Multer is a NodeJS middleware for handling multipart/form-data. It will not process any form which is not multipart (multipart/form-data). To install Multer module, use below command:

npm install multer --save

Follow below segment code to build RestAPIs for handling a uploaded file:

const multer = require('multer');

var storage = multer.diskStorage({
    destination: (req, file, cb) => {
      cb(null, __basedir + '/uploads/')
    },
    filename: (req, file, cb) => {
      cb(null, file.fieldname + "-" + Date.now() + "-" + file.originalname)
    }
});

var upload = multer({storage: storage});

app.post('/api/uploadfile', upload.single("uploadfile"), (req, res) => {
  console.log(req.file);
  res.json({'msg': 'File uploaded successfully!', 'file': req.file});
});

Multer provides a diskStorage engine that we have a full control on storing files to disk.

var storage = multer.diskStorage({
    destination: (req, file, cb) => {
      cb(null, __basedir + '/uploads/')
    },
    filename: (req, file, cb) => {
      cb(null, file.fieldname + "-" + Date.now() + "-" + file.originalname)
    }
});

var upload = multer({storage: storage});

• destination is used to determine within which folder the uploaded files should be stored.
• filename is used to determine what the file should be named inside the folder.

How the below segment code work?

app.post('/api/uploadfile', upload.single("uploadfile"), (req, res) => {
    ...
});

-> Multer adds a file object to the request object. req.file is the uploadfile file.

https://grokonez.com/node-js/multer-build-restapi-to-upload-a-multipartfile-to-nodejs-express