I'd use request for this:
request('http://google.com/doodle.png').pipe(fs.createWriteStream('doodle.png'))
Or if you don't need to save to a file first, and you just need to read the CSV into memory, you can do the following:
var request = require('request');
request.get('http://www.whatever.com/my.csv', function (error, response, body) {
if (!error && response.statusCode == 200) {
var csv = body;
// Continue with your processing here.
}
});
etc.