In Node.js, am I creating a new object when "Require"?

Question

So, what I'm not sure is that. if in ModuleA, I have:

var mongoose = require('mongoose'); mongoose.connect(pathA); 

And in ModuleB, I have:

var mongoose = require('mongoose'); mongoose.connect(pathB); 

And in the main program, I have:

var mA = require('./moduleA.js'),  mB = require('./moduleB.js'); 

So, when I run the main program, I guess I will create two mongoose "instances"; one connecting to pathA and one connecting to pathB, is that right?

Also, in Module B, before I connect to pathB, is it connected to pathA or nothing?

Thanks.

Answer 1

I just did a couple of tests with the latest node V0.4.6. I confirmed the following:

1. The variable returned from "require" is a singleton.
2. Subsequent changes will change the data of the required module among all other modules that include it.
3. Mongoose's connection is a bit weird. Even if you disconnect and set it to a new connection path, it still uses the old connection path.

So, what I mean by the above points 1 and 2 is:

If you have a Module Master:

var myStr = 'ABC'; module.exports.appendStr = function(data) {     myStr += ' ' + data;     }; module.exports.output = function() {     console.log("Output: " + myStr); }; 

And if you have two other modules:

Module A

var mc = require('./moduleMaster.js'); var ma = function() {mc.appendStr(' MA '); }; ma.prototype.output = function() {   mc.output(); } module.exports.create = function() {     return new ma(); };  module.exports._class = ma; 

Module B

var mc = require('./moduleMaster.js'); var mb = function() {mc.appendStr(' MB '); }; ma.prototype.output = function() {   mc.output(); } module.exports.create = function() {     return new mb(); };  module.exports._class = mb; 

Now when you run a test script that requires both Module A and Module B, instantiate them and output:

mTestA.output(); mTestB.output(); 

You will get the following output:

ABC MA ABC MA MB 

instead of

ABC MA ABC MB 

Therefore, it is a singleton. not just local to the module.