NodeJS Basic Tutorial

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NodeJS Buffer & URL;

NodeJS MySql

NodeJS MongoDB

NodeJS File (FS)

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Node.js Multi-process

Comprehensive Examples of Node.js

Node.js Example

Node.js Example：We will useNode.jsTo introduce the basics, examples of fs module, mysql module, http module, url module, parsing JSON, etc.

Below is the list of Node.js examples we will introduce in this Node.js tutorial:

Module/Topic	Examples
Basics	Node.js Example HelloWorld Node.js Example Create a Module
File System	Node.js Example Create a File Node.js Example Read a File Node.js Example　 Write to a File Node.js Example　 Delete a File
MySQL	Node.js Example Connect to MySQL Database Node.js Example SELECT FROM Table Node.js Example SELECT from Table with WHERE clause Node.js Example ORDER entries BY a column Node.js Example INSERT entries INTO Table Node.js Example UPDATE Table Entries Node.js Example DELETE Table Entries Node.js Example Using Result Object
URL	Node.js Example Parse URL Parameters
JSON	Node.js Example Parse JSON File
HTTP	Node.js Example Create HTTP Web Server

Node.js example: Simple Node.js example

Here is a simpleNode.js example,Used to print messages to the console

verifyNode.js

console.log("Hi there! This is Node.js!")

Calculator.js

//　Returns the sum of two numbers
exports.add = function(a, b) {　
　　　　return a+b;　
　};　　
　
//　Returns the difference between two numbers
exports.subtract = function(a, b) {　
　　　　return a-b;　
　};　　
　
//　Returns the product of two numbers
exports.multiply = function(a, b) {　
　　　　return a*b;　
　};

moduleExample.js

var calculator = require('')/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));

readFileExample.js

//　Import the file fs module
var fs = require('fs');　
var data = 'Learn Node FS module';　
　
//　The writeFile function with filename, content, and callback
fs.writeFile('newfile.txt', data, function(err) {　
　　if (err) throw err;　
　　console.log('File is created successfully.');　
　});

Run the program using the node command at the terminal or command prompt:

Terminal output

$ node createFileExample.js
File is created successfully.

This file should be created next to the example node.js program with the content 'Learning Node FS module'.

Node.js Example: Read a file

readFileExample.js

//　Import the file system module
var fs = require('fs');　
　
//　Read the file sample.html
fs.readFile('sample.html',　
　　　　//　Callback function called when the file reading is completed
　　　　function(err, data) {　　
　　　　　　　　if (err) throw err;　
　　　　　　　　//　The data is a buffer containing the file content
　　　　　　　　8)　
　});

Run the program using the node command at the terminal or command prompt:

Terminal output

$ node readFileExample.js
<html>
<body>
<h1>Header</h/h1>
<p>I have learnt to read a file in Node.js.</p>/p>
</body>
</html>

Node.js Example: Delete a file

Ensure there is a file named 'sample.txt' next to the node.js example program.

deleteFile.js

//　Import the fs module
var fs = require('fs');　
　
//　Delete the file named 'sample.txt'
fs.unlink('sample.txt', function(err) {　
　　　　if (err) throw err;　
　　　　//　If there are no errors, the file has been successfully deleted
　　　　console.log('File deleted!');　
　});

Run the program using the node command at the terminal or command prompt:

Terminal output

$ node deleteFile.js
File deleted!

File has been successfully deleted.

Node.js example: Write file

In this example, we will write the content "Hello！” to the text file sample.txt.

nodejs write file example.js

//　Import the file system module
　
var fs = require('fs');　
　
var data = "Hello !"
　
//　Write data to file sample.html
fs.writeFile('sample.txt',data,　
　　　　//　Callback function called after writing to the file
　　　　function(err) {　　
　　　　　　　　if (err) throw err;　
　　　　　　　　//　If there is no error
　　　　　　　　console.log("Data is written to file successfully.")　
　});

When the above program is run in Terminal,

Program output

arjun@arjun-VPCEH26EN:~/workspace/nodejs$ node nodejs-write-to-file-example.js　
Data is written to file successfully.

NodeJS example - Connect to MySQL database

connectToMySQL.js-Connect to MySQL database in Node.js

//　import mysql module
var mysql = require('mysql');　
　
//　create a connection variable with the required details
var con = mysql.createConnection({　
　　host: "localhost",　//　IP address of the server running mysql
　　user: "arjun",　//　mysql database username
　　password: "password"　//　corresponding password
　});　
　
//　Connect to the database.
con.connect(function(err) {　
　　if (err) throw err;　
　　console.log("Connected!");　
　});

selectFromTable.js Simple example of MySQL SELECT FROM query

//　Node.js MySQL SELECT FROM query example
//　import mysql module
var mysql = require('mysql');　
　
//　create a connection variable with the required details
var con = mysql.createConnection({　
　　host: "localhost",　//　IP address of the server running mysql
　　user: "arjun",　//　mysql database username
　　password: "password",　//　corresponding password
　　database: "studentsDB"　//　Use the specified database
　});　
　
//　Establish a connection with the database.
con.connect(function(err) {　
　　if (err) throw err;　
　　//　If the connection is successful
　　con.query("SELECT　*　FROM students", function (err, result, fields) {　
　　　　//　If any error occurs while executing the above query, throw an error
　　　　if (err) throw err;　
　　　　//　If there are no errors, you will get the result
　　　　console.log(result);　
　　});　
　});

selectFromWhere.js

//　import mysql module
var mysql = require('mysql');　
　
//　create a connection variable with the required details
var con = mysql.createConnection({　
　　host: "localhost",　//　IP address of the server running mysql
　　user: "arjun",　//　mysql database username
　　password: "password",　//　corresponding password
　　database: "studentsDB"　//　Use the specified database
　});　
　
//　Establish a connection with the database.
con.connect(function(err) {　
　　if (err) throw err;　
　　//　If the connection is successful
　　con.query("SELECT　*　FROM students WHERE marks>90　
　　　　//　If any error occurs while executing the above query, throw an error
　　　　if (err) throw err;　
　　　　//　If there are no errors, you will get the result
　　　　console.log(result);　
　　});　
　});

Open a terminal from the location of the above .js file, then run the selectFromWhere.js Node.js MySQL example program.

AscOrderExample.js

//import mysql module
var mysql = require('mysql');　
　
//　create a connection variable with the required details
var con = mysql.createConnection({　
　　host: "localhost",　//　IP address of the server running mysql
　　user: "arjun",　//　mysql database username
　　password: "password",　//　corresponding password
　　database: "studentsDB"　//　Use the specified database
　});　
　
//　Establish a connection with the database.
con.connect(function(err) {　
　　if (err) throw err;　
　　//　If the connection is successful
　　con.query("SELECT　*　FROM students ORDER BY marks　
　　　　//　If any error occurs while executing the above query, throw an error
　　　　if (err) throw err;　
　　　　//　If there are no errors, you will get the result
　　　　console.log(result);　
　　});　
　});

Run the above Node.js MySQL ORDER BY example program.

//　import mysql module
var mysql = require('mysql');　
　
//　create a connection variable with the required details
var con = mysql.createConnection({　
　　host: "localhost",　//　IP address of the server running mysql
　　user: "arjun",　//　mysql database username
　　password: "password",　//　corresponding password
　　database: "studentsDB"　//　Use the specified database
　});　
　
//　Establish a connection with the database.
con.connect(function(err) {　
　　if (err) throw err;　
　　//　If the connection is successful
　　con.query("INSERT INTO students (name,rollno,marks) values ('Anisha',12,95function (err, result, fields) {　
　　　　//　If any error occurs while executing the above query, throw an error
　　　　if (err) throw err;　
　　　　//　If there are no errors, you will get the result
　　　　console.log(result);　
　　});　
　});

Run the Node.js MySQL program in the terminal above.

UpdateRecordsFiltered.js-Update records in MySQL table

//　import mysql module
var mysql = require('mysql');　
　
//　create a connection variable with the required details
var con = mysql.createConnection({　
　　host: "localhost",　//　IP address of the server running mysql
　　user: "arjun",　//　mysql database username
　　password: "password",　//　corresponding password
　　database: "studentsDB"　//　Use the specified database
　});　
　
//　Establish a connection with the database.
con.connect(function(err) {　
　　if (err) throw err;　
　　//　If the connection is successful
　　con.query("UPDATE students SET marks=84　WHERE marks=74", function (err, result, fields) {　
　　　　//　If any error occurs while executing the above query, throw an error
　　　　if (err) throw err;　
　　　　//　If there are no errors, you will get the result
　　　　console.log(result);　
　　});　
　});

Run the above program in the terminal

Terminal output

arjun@arjun-VPCEH26EN:~/workspace/nodejs$ node UpdateRecordsFiltered.js　
OkPacket {　
　　fieldCount: 0,　
　　affectedRows:　3,　
　　insertId: 0,　
　　serverStatus:　34,　
　　warningCount: 0,　
　　message: '(Rows matched:　3　　Changed:　3　　Warnings: 0',　
　　protocol41: true,　
　　changedRows:　3　}

Node.js example – deleting table entries

Execute DELETE FROM query on the specified table when one or more properties on the table are filtered.

deleteRecordsFiltered.js

　//　import mysql module　
　var mysql = require('mysql');　
　
　//　create a connection variable with the required details　
　var con = mysql.createConnection({　
　　host: "localhost",　//　IP address of the server running mysql　
　　user: "arjun",　//　mysql database username
　　password: "password",　//　corresponding password
　　database: "studentsDB"　//　Use the specified database
　});　
　
　//　Connect to the database.　
　con.connect(function(err) {　
　　if (err) throw err;　
　　//　If the connection is successful　
　　con.query("DELETE FROM students WHERE rollno>"10", function (err, result, fields) {　
　　　　//　If any error occurs while executing the above query, throw an error　
　　　　if (err) throw err;　
　　　　//　If there are no errors, you will get the result　
　　　　console.log(result);　
　　});　
　});

Run deleteRecordsFiltered.js-Terminal output

arjun@arjun-VPCEH26EN:~/workspace/nodejs$ node deleteRecordsFiltered.js　
OkPacket {　
　　fieldCount: 0,　
　　affectedRows:　6,　
　　insertId: 0,　
　　serverStatus:　34,　
　　warningCount: 0,　
　　message: '',　
　　protocol41: true,　
　　changedRows: 0}

Node.js example – using result objects

We can use the DOT (.) operator to access records in the result set as arrays and as properties of records.

selectUseResultObject.js-Access row and column data in the result set

//　Node.js MySQL result object example
//　import mysql module
var mysql = require('mysql');　
　
//　create a connection variable with the required details
var con = mysql.createConnection({　
　　host: "localhost",　//　IP address of the server running mysql
　　user: "arjun",　//　mysql database username
　　password: "password",　//　corresponding password
　　database: "studentsDB"　//　Use the specified database
　});　
　
//　Establish a connection with the database.
con.connect(function(err) {　
　　if (err) throw err;　
　　//　If the connection is successful
　　con.query("SELECT　*　FROM students", function (err, result, fields) {　
　　　　//　If any error occurs while executing the above query, throw an error
　　　　if (err) throw err;　
　　　　//　If there are no errors, you will get the result
　　　　//　Iterate over all rows in the result
　　　　Object.keys(result).forEach(function(key) {　
　　　　　　var row = result[key];　
　　　　　　console.log(row.name)　
　　　　});　
　　});　
　});

Run the above program using the node in the terminal

Terminal output

arjun@arjun-VPCEH26EN:~/workspace/nodejs$ node selectUseResultObject.js　
John
Arjun
Prasanth
Adarsh
Raja
Sai
Ross
Monica
Lee
Bruce
Sukumar

Node.js Example – Parsing URL Parameters

urlParsingExample.js-Node.js program that parses the URL into readable parts in Node.js

//　Import the url module
var url = require('url');　
var address = 'http://localhost:8080/index.php?type=page&action=update&id=5221";　
var q = url.parse(address, true);　
　
console.log(q.host);　//Returns 'localhost:8080
console.log(q.pathname);　//Returns/index.php
console.log(q.search);　//returns '?type=page&action=update&id=5221"
　
var qdata = q.query;　//　Returns an object: {Type: page, Operation: 'update', id = '"5221}
console.log(qdata.type);　//Returns "page"
console.log(qdata.action);　//Returns "update"
console.log(qdata.id);　//Returns "　5221"

Terminal output

$ node urlParsingExample.js　
localhost:8080
/index.php
　?type=page&action=update&id=5221
page
update
5221

Node.js Example: Parse JSON File

The following examples can help you use the JSON.parse() function and access elements from the JSON object.

nodejs-parse-json.js

//　JSON data
var jsonData = '{"persons":[{"name":"John","city":"New York"},{"name":"Phil","city":"Ohio"}]}';　
　
//　Parse json
var jsonParsed = JSON.parse(jsonData);　
　
//　Access element
console.log(jsonParsed.persons[0].name);

Run nodejs-parse-Terminal output of json.js

　
arjun@arjun-VPCEH26EN:~/workspace/nodejs$ node nodejs-parse-json.js　
John

Node.js Example: Create HTTP Web Server

Node.js Example – An HTTP Web Server that prepares responses with HTTP headers and messages.

//　Import the http module in the file
var http = require('http');　
　
//　Create a server
http.createServer(function (req, res) {　
　　　　//　HTTP headers
　　　　//　200-Confirm message
　　　　//　To use html content for the response, "Content-Type" should be "text　/　html"
　　　　res.writeHead(200, {'Content-Type': 'text/html'});　　
　　　　res.write('Node.js says hello!');　//Write a response to the client
　　　　res.end();　//End of response
　}).listen(9000);　//The server object is listening on port9000 is listening

Run the server

$ node httpWebServer.js

Open the browser and click the URL "http://127.0.0.1:9000/to trigger requests to our web server.

Node.js Multi-process