module.exports vs exports in Node.js

Question

I\'ve found the following contract in a Node.js module:

module.exports = exports = nano = function database_module(cfg) {...}

I wonder what

Answer 1

1. Both module.exports and exports point to the same function database_module(cfg) {...}.

   1| var a, b;
   2| a = b = function() { console.log("Old"); };
   3|     b = function() { console.log("New"); };
   4|
   5| a(); // "Old"
   6| b(); // "New"
   

   You can change b on line 3 to a, the output is reverse. The conclusion is:

   a and b are independent.

2. So module.exports = exports = nano = function database_module(cfg) {...} is equivalent to:

   var f = function database_module(cfg) {...};
   module.exports = f;
   exports = f;
   

   Assumed the above is module.js, which is required by foo.js. The benefits of module.exports = exports = nano = function database_module(cfg) {...} is clear now:

   • In foo.js, since module.exports is require('./module.js'):

     var output = require('./modules.js')();
     

   • In moduls.js: You can use exports instead of module.exports.

So, you will be happy if both exports and module.exports pointing to the same thing.