NodeJs Session02

Workshop
@
Ramnshee Infotech
By Jainul Musani
SESSION:02
2

Node.js Package Manager - NPM
 Node Package Manager provides two main
functionalities:
 It provides online repositories for node.js
packages/modules which are searchable on
search.nodejs.org
 It also provides command line utility to install
Node.js packages, do version management and
dependency management of Node.js packages.
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Node.js Package Manager - NPM
 The npm comes bundled with Node.js installables in versions
after that v0.6.3. You can check the version by opening
Node.js command prompt and typing the following
command:
> npm version
C:UsersJamtemp>npm version
{
npm: '6.14.4',
ares: '1.16.0',
brotli: '1.0.7',
cldr: '37.0',
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http_parser: '2.9.3',
icu: '67.1',
llhttp: '2.0.4',
modules: '72',
napi: '6',
nghttp2: '1.40.0',
node: '12.17.0',
openssl: '1.1.1g',
tz: '2019c',
unicode: '13.0',
uv: '1.37.0',
v8: '7.8.279.23-node.37',

Installing Modules using npm
 Syntax:
npm install <Module Name>
Example:
npm install express
 Global vs Local Installation
npm install express -g
 Uninstalling a Module
npm uninstall express
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Searching a modules using npm
 Syntax:
npm search <Module Name>
Example:
npm search express
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Node.js Module Types
 Node.js includes three types of modules:
1. Core Modules
2. Local Modules
3. Third Party Modules
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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 compiled into its binary
distribution and load automatically when Node.js
process starts.
 You need to import the core modules first in order
to use it in your application.
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Core Module Description
http http module includes classes, methods and events to create
Node.js http server.
url url module includes methods for URL resolution and parsing.
querystring querystring module includes methods to deal with query
string.
path path module includes methods to deal with file paths.
fs fs module includes classes, methods, and events to work
with file I/O.
util util module includes utility functions useful for
programmers.
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SESSION:02
 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.

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 The following example demonstrates how to use Node.js
http module to create a web server.
var http = require('http');
var server =
http.createServer(function(req, res)
{
res.writeHead(200,{'Content-Type': 'text/html'});
res.write('Node.js says hello!');
res.end();
});
server.listen(5000);

Node.js Local Modules
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 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.
 For example, if you need to connect to MongoDB and
fetch data then you can create a module for it, which
can be reused in your application.

Writing Simple Module
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var greet= {
morning: function (msg) {
console.log(‘Good Morning: Mr. ' + msg);
},
afternoon:function (msg) {
console.log(‘Good Afternoon Mr. ' + msg);
},
evening:function (msg) {
console.log(‘Good Evening Mr. ' + msg);
}
};
module.exports = greet

Node.js Local Modules
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 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,
object or variable as a module in Node.js.
app.js
var mygreet = require('./greet.js');
mygreet.morning(‘Sachin');

Export Module in Node.js
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 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 you assign to module. exports will
be exposed as a module.

Export Literals
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 As exports is an object. It exposes whatever you
assigned to it as a module.
 For example, if you assign a string literal then it
will expose that string literal as a module.

Export Object
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 The exports is an object.
 So, you can attach properties or methods to it.

Export Function as a Class
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Load Module from a Separate Folder
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Use the full path of a module file where you have
exported it using module.exports.
For example, if the mylib module in the Jlib.js is
stored under the utility folder under the root folder
of your application, then import it, as shown below.
var mylib = require('./utility/Jlib.js');

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example:
Create a calculator.js in ‘temp’ folder
// Returns addition of two numbers
exports.add = function (a, b) {
return a+b;
};
exports.subtract = function (a, b) {
return a-b;
};
exports.multiply = function (a, b) {
return a*b;
};

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example:
Create a moduleExample.js outside ‘temp’ folder
var calculator = require('./temp/calculator');
var a=10, b=5;
console.log("Addition : "+calculator.add(a,b));
console.log("Subtraction : "+calculator.subtract(a,b));
console.log("Multiplication : "+calculator.multiply(a,b));

How to extend the existing module
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Extend or add functions to Node.js module
Steps:
1. Include the module
2. Add function to the module variable
3. Re-export the module
Example: Creating a new .js file myExt.js
var calc = require(‘./calculator');
calc.divide = function(a,b){
return a/b;
};
module.exports = calc;

Override function of a Node.js module
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Extend or add functions to Node.js module
Steps:
1. Include the module
2. Delete function from the module variable.
3. Add the function with the same name to the module variable
4. Re-export the module
Example: overriding a function in the file myExt.js
var calc = require(‘./calculator');
delete calc[‘divide’];
calc.divide = function(a,b){
console.log(‘New Func Added’);
return a/b;
};
module.exports = calc;

NodeJs Session02

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NodeJs Session02