# Understanding Modules And Its Type In NodeJS

What is a Module in Node.js?
----------------------------

In NodeJS, every JS file is a `module`.

Consider `modules` to be the same as JavaScript libraries. A set of functions, variables, you want to include in other JS files (modules) of your application.

Built-in Modules
----------------

Node.js has a set of built-in modules which you can use without any further installation.

Include Modules
---------------

To include a module, use the `require()` function with the name of the module:

```
var http = require('http');
```

Now your application has access to the HTTP module, and is able to create a server:

```
http.createServer(function (req, res) {

  res.writeHead(200, {'Content-Type': 'text/html'});

  res.end('Hello World!');

}).listen(3000);

```

Create Your Own Modules
-----------------------

You can create your `own modules`, and easily include them in your applications.

The following example creates a module that returns a `date` and `time` object:

```
exports.myDateTime = function () {

  return Date();

};
```

Use the `exports` keyword to make properties and methods available outside the module file.

Save the code above in a file called `"myfirstmodule.js"`

Include Your Own Module
-----------------------

Now you can include and use the module in any of your Node.js files.

```
var http = require('http');

var dt = require('./myfirstmodule');

http.createServer(function (req, res) {

  res.writeHead(200, {'Content-Type': 'text/html'});

  res.write("The date and time are currently: " + dt.myDateTime());

  res.end();

}).listen(3000);
```

Notice that we use `./` to locate the module, that means that the module is located in the `same` folder as the Node.js file, if you want to go one folder up use `../`

Save the code above in a file called "`demo_module.js`", and run the file:

```
node demo_module.js
```

If you have followed the same steps on your computer, you will see the same result as the example: <http://localhost:3000>

`So In this section, We saw types of Modules in Javascript and how to use them in different situations.`