What is the difference between these two kind of requiring in Javascript?

Question

In a tutorial I saw a code like this:

var session = require('express-session');
var FileStore = require('session-file-store')(session);

And another code like this:

var mongoose = require('mongoose');
var Schema = mongoose.Schema;

But I think I can write the first code like this:

var sessionFileStore = require('session-file-store');
var FileStore = sessionFileStore.session;

And the second one like:

var Schema = require('mongoose')(Schema);

OR

var Schema = require('mongoose').Schema;

I just wanted to ask for sure, are these two kind of writing equal or there are some differences?

I also like to know what is the meaning/difference if I use something like below for the second command:

var Schema = require('mongoose')('Schema');

Answer 1

It is the same. require is a normal function, which returns a value. So, if that value is also a function, you can immediately call it, or use one of its properties if it is an object.

However, in the second case, require('mongoose')(Schema) will cause two errors:

1. Here require returns an object, not a function, so you can't invoke it.
2. You are using the variable Schema which has not been defined yet, and passing it as an argument to a function.

In the second case, the right way to put it in a single line is var Schema = require('mongoose').Schema;

And in the first case, I think that the correct way is var FileStore = sessionFileStore(session); I assume here session is a global variable, or has been defined previously.