Node JS Module Types and Tutorials

Node Module Types

Node.js modules are generally categorized by 3 Types.

1.     Core Modules

2.     Local Modules

3.     Third Party Modules

Node.js Core Modules:

Node.js is a light weight framework. The core modules include bare minimum functionalities of Node.js. These core modules are load automatically when Node.js process starts.

However, you need to import the core module first in order to use it in your application.

Loading Core Modules:

In order to use Node.js core or NPM modules, you first need to import it using require() function as shown below.

var module = require('module_name');

As per above syntax, specify the module name in the require() function. The require() function will return an object, function, property or any other JavaScript type, depending on what the specified module returns.

Node.js Local Module:

Local modules are modules created locally in your Node.js application. These modules include different functionalities of your application in separate files and folders. You can also package it and distribute it via NPM, so that Node.js community can use it.

In Node.js, module should be placed in a separate JavaScript file. So, create a Log.js file and write the following code in it.

In the above example of logging module, we have created an object with three functions - info(), warning() and error(). At the end, we have assigned this object to module.exports. The module.exports in the above example exposes a log object as a module.

The module.exports is a special object which is included in every JS file in the Node.js application by default. Use module.exports or exports to expose a function.

Loading Local Module:

To use local modules in your application, you need to load it using require() function in the same way as core module. However, you need to specify the path of JavaScript file of the module.

In the above example, app.js is using log module. First, it loads the logging module using require() function and specified path where logging module is stored. Logging module is contained in Log.js file in the root folder. So, we have specified the path './Log.js' in the require() function. The '.' denotes a root folder.

The require() function returns a log object because logging module exposes an object in Log.js using module.exports. So now you can use logging module as an object and call any of its function using dot notation e.g myLogModule.info() or myLogModule.warning() or myLogModule.error()

Node.js Third party Module:

The third party module can be downloaded by NPM (Node Package Manager). These type of modules are developed by others and we can use that in our project. Some of the best third party module examples are listed as follows: express, gulp, lodash, async, socket.io, mongoose, underscore, pm2, bower, q, debug, react, etc.,

Third party modules can be install inside the project folder or globally.

Loading Third Party Module:

Third party Node.js module can be downloaded using NPM (node package manager) which you can download locally or globally. To download globally we use the following command.

npm install  <module_name>  -g

here  we use -g to install package globally. If you want to install locally then use the following command.

npm install  <module_name>  --save 

Above command will download node package inside node_modules folder and then you can directly use require function to load node module. 

var module= require('module_name');   

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