CODEWITHSUNDEEP
node.js
pankajt
pankajt

Reputation: 7864

Nodejs - Difference between require('module') and require('module').db?

//module.js
exports.doA = function(callback) {
   db.asyncConnect(/* connect options */, function(err, database) {
       if(err == null) {
           exports.db = database;
       }
   });
}

exports.db = null;

// test1.js
var mydb = require('module');
console.log(mydb);

// test2.js
var db = require('module').db;
console.log(db);

How is var mydb = require('module'); different from var mydb = require('module').db; ?

Update: Updating with the code and behavior I am observing

// file: db.js
exports.init = function (start_server){
    MongoClient.connect(url, {
            db: {
                raw: true
            },
            server: {
                poolSize: 5
            }
        },
        function(err, database) {
            exports.db = database;
            if(err == null)
            start_server();
        }
    );
}

exports.db = null;

.

// file: test.js
var mongodb = require('./db.js');
var db = require('./db.js').db;

console.log("MongoDb " + mongodb.db);
console.log("DB " + db);

Output: MongoDb [object Object] DB null

Q. The variable db is coming out to be null but mongodb.db is having values? Even if I assign the value of mongodb.db in a variable, the value is coming out to be null.

Upvotes: 0

Views: 73

Answers (2)

Henrik Andersson
Henrik Andersson

Reputation: 47202

var mydb = require('module');

This gets the entire module.

var mydb = require('module').db;

This gets the property db of the object that the module returns.

The downside to the latter part is that you can't access the "parent" object anymore, ie. whatever is returned from the .db call, will be what you get and nothing else.

Quick example: 

//some_module.js

var SomeModule = {
    db: function () {
        console.log("hello");
    }
};
module.exports = SomeModule;

//some_other_module.js
var SomeModule = require('./some_module.js');
console.log(SomeModule); // [Object object]

var SomeDB = require('./some_module.js').db;
console.log(SomeDB); // function () {}

Upvotes: 2

Andi N. Dirgantara
Andi N. Dirgantara

Reputation: 2051

It's basically different

var mydb = require('module');

That means every object that you export will be called/ imported. mydb.doA and mydb.db are available.

var db = require('module').db;

Only db object is called/ imported to your code. Different from first example, db it self is like mydb.db in the first example.

Upvotes: 0

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