multer

What is multer?

Multer is a node.js middleware for handling multipart/form-data, which is primarily used for uploading files. It is written on top of busboy for maximum efficiency.

What are multer's main functionalities?

File Uploads

This feature allows you to upload files to your server. The code sample demonstrates how to handle a single file upload with Multer.

const multer = require('multer');
const upload = multer({ dest: 'uploads/' });

app.post('/upload', upload.single('file'), function (req, res) {
  // req.file is the `file` file
  res.send('File uploaded!');
});

Multiple Files Upload

Multer also supports uploading multiple files at once. The code sample shows how to handle multiple file uploads, limiting to 12 files in this case.

const multer = require('multer');
const upload = multer({ dest: 'uploads/' });

app.post('/upload', upload.array('files', 12), function (req, res) {
  // req.files is array of `files` files
  res.send('Multiple files uploaded!');
});

Disk Storage

Multer allows you to customize the storage of files. This code sample demonstrates how to use disk storage to control the storage location and file naming.

const multer = require('multer');

const storage = multer.diskStorage({
  destination: function (req, file, cb) {
    cb(null, 'uploads/')
  },
  filename: function (req, file, cb) {
    cb(null, file.fieldname + '-' + Date.now())
  }
});

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

Memory Storage

For temporary storage or when you want to process the file without saving it to disk, you can use memory storage. The code sample shows how to store a file in memory.

const multer = require('multer');
const upload = multer({ storage: multer.memoryStorage() });

app.post('/upload', upload.single('file'), function (req, res) {
  // req.file is the `file` file stored in memory
  res.send('File uploaded and stored in memory!');
});

File Filtering

Multer provides a way to filter out files based on conditions you set. This code sample demonstrates file filtering to only allow JPEG images.

const multer = require('multer');
const upload = multer({
  fileFilter: function (req, file, cb) {
    if (file.mimetype !== 'image/jpeg') {
      return cb(new Error('Only JPEG files are allowed!'), false);
    }
    cb(null, true);
  }
});

Other packages similar to multer

formidable

Formidable is an alternative to Multer for parsing form data, especially file uploads. It is less middleware-oriented and more flexible in terms of handling various form parsing tasks.

busboy

Busboy is a low-level Node.js module for parsing incoming HTML form data. Multer is built on top of Busboy, but provides a more convenient middleware API for integrating with Express.js applications.

multiparty

Multiparty is another module for handling multipart/form-data requests, which is the type of requests that file uploads usually come in. It is similar to Multer but has a different API and is used in a slightly different way.

README

Multer

Multer is a Connect middleware for handling multipart/form-data