What for at exports function to nest in function in this case?

Question

Node.js

In one module I found this code:

module.exports.authenticate = function(){
  return function(req, res, next){ ... };
}

Why it can't be done like this and why it doesn't work like this:

module.exports.authenticate = function(req, res, next){ ... };

All code in gh

Answer 1

Apparently the author was so comfortable. These are middlewares. In the first case, to pass it where as a parameter, you need to call authenticate (), and in the second, just authenticate