Filter files on the basis of extension using Multer in Express JS

Question

As question title explains, I need to filter uploaded files on the basis of file extension. So, I went through the official docs and searched this website.

What I've Tried

I've tried solutions I came across. Files are being successfully uploaded, but the problem is how to filter files. Currently my Router.js file looks like this.

Router.JS

var multer  = require('multer');
var storage = multer.diskStorage({ //multers disk storage settings
    destination: function (req, file, cb) {
        cb(null, './public/uploads/')
    },
    limits:{
        files: 1,
        fileSize: 1024 * 1024
    },
    filename: function (req, file, cb) {
        var datetimestamp = Date.now();
        cb(null, file.fieldname + '-' + datetimestamp + '.' + file.originalname.split('.')[file.originalname.split('.').length -1])
    },
    onFileUploadStart: function(file) {
        console.log("Inside uploads");
        if (file.mimetype == 'image/jpg' || file.mimetype == 'image/jpeg' || file.mimetype == 'image/png') {
            return true;
        }
        else
        {
            return false;
        }
    }
});
var upload = multer({ //multer settings
    storage: storage
}).single('profilepic');


router.post('/profile', function(req, res){
    upload(req,res,function(err){
        if(err)
        {
            console.log(err);
        }
        else
        {
            console.log("Image was uploaded");
        }
    });
});

I tried echoing something in onFileUploadStart to check if it is going into that function or not. And it was not. Besides onFileUploadStart, I also tried fileFilter as mentioned at this link, but it was not helpful. Any suggestions how to solve this? Thanks in advance.

Answer 1

An example using multer:

var storage = multer.diskStorage({ //multers disk storage settings
    destination: function (req, file, cb) {
        cb(null, './public/uploads/')
    },
    filename: function (req, file, cb) {
        var datetimestamp = Date.now();
        cb(null, file.fieldname + '-' + datetimestamp + '.' + file.originalname.split('.')[file.originalname.split('.').length -1])
    }
});

var upload = multer({ //multer settings
    storage: storage,
    fileFilter: function (req, file, callback) {
        var ext = path.extname(file.originalname);
        if(ext !== '.png' && ext !== '.jpg' && ext !== '.gif' && ext !== '.jpeg') {
            return callback(new Error('Only images are allowed'))
        }
        callback(null, true)
    },
    limits:{
        fileSize: 1024 * 1024
    }
}).single('profilepic');

Excerpted from Node.js - File upload. The original authors were Iceman and Mikhail. Attribution details can be found on the contributor page. The source is licenced under CC BY-SA 3.0 and may be found in the Documentation archive. Reference topic ID: 4080 and example ID: 14210.

Answer 2

If you are used to web development, you can be validated at the front end, not passed to the back end，you can try：

var file = files[0];  
var imageType = /image.*/;  

if (!file.type.match(imageType)) {  
     // do something  
}