Download a file from NodeJS Server using Express

Question

How can I download a file from my server to a computer that is browsing a nodeJS server page?

I'm using ExpressJS and have been experimenting with the following:

app.get('/download', function(req, res){

  var file = fs.readFileSync(__dirname + '/upload-folder/dramaticpenguin.MOV', 'binary');

  res.setHeader('Content-Length', file.length);
  res.write(file, 'binary');
  res.end();
});

But I can't get the file name and the file type ( or extension ). Can anyone help me with that?

Answer 1

Because the file's name is just 'download' in your browser's eyes, you'll need to offer it extra information by using another HTTP header.

res.setHeader('Content-disposition', 'attachment; filename=dramaticpenguin.MOV');

You may also want to send a mime-type such as this:

res.setHeader('Content-type', 'video/quicktime');

If you want something more in-depth, here ya go.

var path = require('path');
var mime = require('mime');
var fs = require('fs');

app.get('/download', function(req, res){

  var file = __dirname + '/upload-folder/dramaticpenguin.MOV';

  var filename = path.basename(file);
  var mimetype = mime.lookup(file);

  res.setHeader('Content-disposition', 'attachment; filename=' + filename);
  res.setHeader('Content-type', mimetype);

  var filestream = fs.createReadStream(file);
  filestream.pipe(res);
});

You may change the header value to anything you like. In this scenario, I'm checking the file's mime-type with a mime-type library called node-mime.

Another thing to keep in mind is that I've switched your code to utilise a readStream. Because node is designed to be asynchronous, employing any method with the word 'Sync' in the name is frowned upon.

To make things easier, Express includes a tool for this.

http://expressjs.com/en/api.html#res.download

app.get('/download', function(req, res){
  const file = `${__dirname}/upload-folder/dramaticpenguin.MOV`;
  res.download(file); // Set disposition and send it.
});