What do “module.exports” and “exports.methods” mean in NodeJS / Express?

Question

Looking at a random source file of the express framework for NodeJS, there are two lines of the code that I do not understand (these lines of code

Answer 1

Module's code is wrapped in module.exports (The module, maybe composed by other module). There are many ways to build a module, but this is one very common (and my personal favorite).

// Dependencies
// const module = require('module');

// Module object
var foo = {}

// Internal property
foo._a = 'a';

// "Public" property
foo.b = 'b';

// Method
foo.fu = function() { return 'fu' };

// Export
module.exports = foo;