如何验证使用 multer 上传的最少文件数？

Question

I want to upload files with multer, but I need that if less than 3 files are loaded simultaneously it shows an error and does not save them on my server. I know how to limit a maximum number of files, but I don't know how to limit a minimum number of files. This is my Multer configuration

const multer = require('multer');

function uploadFile() {
  const storage = multer.diskStorage({
    destination: './public/files',
    filename: function (_req, file, cb) {
          var extension = file.originalname.slice(file.originalname.lastIndexOf('.'));
           cb(null, Date.now() + extension);
        }
      }); 
      const upload = multer({ 
        storage, 
        limits: {fileSize: 11657128, files: 3},
        fileFilter: function(req, file, cb) {
          let type = req.files
          type?cb(null, true):cb(new Error ('no es un archivo de tipo texto plano'));
        }}
      ).array('file');
      return upload;
}

module.exports = uploadFile;

Answer 1

You can add a middleware or a validation at your routes.

app.post('/your/route', upload.array('field', 3), function (req, res) {
  if (req.files.length !== 3) {
    return res.status(400).json({ error: 'Three files is required'})
  }
})

With array of middleware:

function validUploadLength (req, res, next) {
  if (req.files.length !== 3) {
    return res.status(400).json({ error: 'Three files is required'})
  }
  next()
}

app.post('/your/route', [upload.array('field', 3), validUploadLength], function (req, res) {
  /// Your code
})