[Episode two] NodeJS Modules for web development

What is a Module in Node.js?

Consider modules to be the same as JavaScript libraries. A set of functions you want to include in your application that would help perform some special functions too.

Built-in Modules

Node.js has a set of built-in modules that 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(8080);

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:

Example

Create a module that returns the current date and time:

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.

Example

Use the module “myfirstmodule” in a Node.js file:

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(8080);
Notice that we use ./ to locate the module, which means that the module is located in the same folder as the Node.js file.

Save the code above in a file called “demo_module.js”, and initiate the file:

Initiate demo_module.js:
C:\Users\Your Name>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:8080

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