multer-s3-middleware.js

var AWS = require('aws-sdk')
var multer = require('multer')
var multerS3 = require('multer-s3')

AWS.config.loadFromPath('./s3_config.json')
var s3 = new AWS.S3()

var upload = multer({
  storage: multerS3({
    s3: s3,
    bucket: 'YOUR-BUCKET-NAME',
    acl: 'public-read',
    metadata: function (req, file, cb) {
      cb(null, {fieldName: file.fieldname});
    },
    key: function (req, file, cb) {
      cb(null, Date.now().toString()+"-"+file.originalname)
    }
  })
});

module.exports = upload;