1. Prepared By:
Prof. Bareen Shaikh
Department of Computer
Science,
MIT ACSC,ALNDI(D), PUNE
NodeJs Modules
2. Topics
3.3 Module and ModuleTypes
3.4 Core Module, Local Module
3.5 Directories as module
3.5 Module. exports
3. Module and Module Types
Module in Node.js is a simple or complex functionality organized in
single or multiple JavaScript files which can be reused throughout the
Node.js application.
Each module in Node.js has its own context, so it cannot interfere with
other modules or pollute global scope.
Each module can be placed in a separate .js file under a separate folder.
Node.js ModuleTypes: Node.js includes three types of modules:
1. Core Modules
2. Local Modules
4. Core Module
Node.js is a light weight framework.
The core modules include bare minimum functionalities of Node.js.
These core modules are compiled into its binary distribution and load
automatically when Node.js process starts.
Need to be import the core module first in order to use in an
application.
Following lists some of the important core modules in Node.js
http
url
util
path
fs
5. Loading Core Module
In order to use Node.js core or NPM modules, need to import it
using require() function as shown below.
var module = require('module_name');
require() function return an object, function, property or any other
JavaScript type, depending on what the specified module returns.
Eg.
var http = require('http');
var server = http.createServer(function(req, res){
//write code here
}); server.listen(5000);
6. Local Module
Local modules are modules created locally by user in Node.js
application.
Modules may include different functionalities of application in
separate files and folders.
These module can also package it and distribute it via NPM, so that
Node.js community can use it.
For example,
If an application need to connect to MongoDB and fetch data then user
can create a module for it, which can be reused in many application that
are requiring it.
7. Creating Local Module
File name suppose module_calc.js which consists of following code.
function add(a,b){
return(a+b)
}
module.exports=add
Create another file calculator.js which consists of following code.
var req=require('./module_cal.js');
result=req(5,4)
console.log("output is"+result);
8. Export Module
The module.exports is a special object which is included in every
JavaScript file in the Node.js application by default.
The module is a variable that represents the current module,
and exports is an object that will be exposed as a module.
So, whatever assign to module.exports will be exposed as a module.
Different types as a module using module.exports
Exports Literals
Export Object
Export Function
9. Export Literals
Assigning a string literal then it will expose that string literal as a
module.
Suppose following code is written in mod.js file
module.exports = 'Hello world‘;
In another app.js file following code is written
var msg = require('./mod.js');
console.log(msg);
10. Export Object
Exports is an object. So, can attach properties or methods to it.
Suppose following code is written in mod.js file
exports.SimpleMessage = 'Hello world';
In another app.js file following code is written
var msg = require('./mod.js');
console.log(msg.SimpleMessage);
11. Attach Object to module.exports
Suppose following code is written in mod.js file
module.exports = {
firstName:‘Bareen',
lastName:‘Shaikh’
}
In another app.js file following code is written
var msg = require('./mod.js');
console.log(msg.firstName + ' ' + msg.lastName);
12. Export Function
Can attach an anonymous function to exports object as shown below
Suppose following code is written in mod.js file
module.exports = function (msg) {
console.log(msg);
};
In another app.js file following code is written
var msg = require('./mod.js');
msg('HelloWorld');
13. Export Function as Class
In JavaScript, a function can be treated like a class.
Suppose following code is written in mod.js file
module.exports = function (firstName, lastName) {
this.firstName = firstName;
this.lastName = lastName;
this.fullName = function () {
return this.firstName + ' ' + this.lastName;
}
}
In another app.js file following code is written
var req= require('./mod.js');
var person = new req(‘Bareen',‘Shaikh');
console.log(person.fullName());
