Double underscore in front of a variable

Question

I have the following code snippet in my node code.

var fs = require('fs');

fs.readdir(__dirname, function (err, files) {
    console.log(files);
});

Why does the variable '__dirname' have double underscores? I know that one underscore is a naming convention for a private/protected variable... but does double underscore mean something more?

Answer 1

__dirname and __filename are local to each module but with the particularity that are strings.

http://nodejs.org/docs/latest/api/globals.html

documentation specifies:

__dirname isn't actually a global but rather local to each module.

and normally underscore means private ( In Javascript, what does this underscore mean? )

It can be interpreted as a local private variable to the module.