Node.js Examples

Node.js Examples : We shall go through examples of basics, fs module, mysql module, http module, url module, parsing json, etc. with Node.js.

Following is the list of Node.js Examples.

Node.js Example 1 – Simple Node.js Example

Following is a simple Node.js Example to print a message to console.

helloworld.js

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console.log("Hello World!")

Output

$ node helloworld.js 
Hi there! This is Node.js!

Node.js Example – Create a Module

Following is Node.js Example where we create a Calculator Node.js Module with functions add, subtract and multiply. And use the Calculator module in another Node.js file.

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// Returns addition of two numbers
exports.add = function (a, b) {
    return a+b;
}; 

// Returns difference of two numbers
exports.subtract = function (a, b) {
    return a-b;
}; 

// Returns product of two numbers
exports.multiply = function (a, b) {
    return a*b;
};

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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));

$ node moduleExample.js 
Addition : 15
Subtraction : 5
Multiplication : 50

Node.js Example – Create a File

Following Node.js Example creates a file with data provided.

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// include node fs module
var fs = require('fs');
var data ='Learn Node FS module';

// writeFile function with filename, content and callback function
fs.writeFile('newfile.txt', data, function (err) {
  if (err) throw err;
  console.log('File is created successfully.');
});

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

$ node createFileExample.js
File is created successfully.

The file should be created next to your example node.js program with the content ‘Learn Node FS module’.

Node.js Example – Read a File

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// include file system module
var fs = require('fs');

// read file sample.html
fs.readFile('sample.html',
	// callback function that is called when reading file is done
	function(err, data) {		
		if (err) throw err;
		// data is a buffer containing file content
		console.log(data.toString('utf8'))
});

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

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

Node.js Example – Delete a File

make sure there is a file named ‘sample.txt’ next to the node.js example program.

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// include node fs module
var fs = require('fs');

// delete file named 'sample.txt'
fs.unlink('sample.txt', function (err) {
	if (err) throw err;
	// if no error, file has been deleted successfully
	console.log('File deleted!');
});

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

$ node deleteFile.js
File deleted!

The file is successfully deleted.

Node.js Example – Write to a File

In this example, we shall write content, “Hello !” , to a text file sample.txt.

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// include file system module

var fs = require('fs');

var data = "Hello !"

// write data to file sample.html
fs.writeFile('sample.txt',data,
	// callback function that is called after writing file is done
	function(err) {		
		if (err) throw err;
		// if no error
		console.log("Data is written to file successfully.")
});

When the above program is run in Terminal,

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

NodeJS Example – Connect to MySQL Database

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// include mysql module
var mysql = require('mysql');

// create a connection variable with the details required
var con = mysql.createConnection({
  host: "localhost",	// ip address of server running mysql
  user: "arjun",	// user name to your mysql database
  password: "password"	// corresponding password
});

// connect to the database.
con.connect(function(err) {
  if (err) throw err;
  console.log("Connected!");
});

$ node connectToMySQL.js 
Connected!

NodeJS Example – SELECT FROM Table

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// Node.js MySQL SELECT FROM query Example
// include mysql module
var mysql = require('mysql');

// create a connection variable with the required details
var con = mysql.createConnection({
  host: "localhost",	// ip address of server running mysql
  user: "arjun",	// user name to your mysql database
  password: "password",	// corresponding password
  database: "studentsDB" // use the specified database
});

// make to connection to the database.
con.connect(function(err) {
  if (err) throw err;
  // if connection is successful
  con.query("SELECT * FROM students", function (err, result, fields) {
	// if any error while executing above query, throw error
    if (err) throw err;
	// if there is no error, you have the result
    console.log(result);
  });
});

$ node selectFromTable.js 
[ RowDataPacket { name: 'John', rollno: 1, marks: 74 },
  RowDataPacket { name: 'Arjun', rollno: 2, marks: 74 },
  RowDataPacket { name: 'Prasanth', rollno: 3, marks: 77 },
  RowDataPacket { name: 'Adarsh', rollno: 4, marks: 78 },
  RowDataPacket { name: 'Raja', rollno: 5, marks: 94 },
  RowDataPacket { name: 'Sai', rollno: 6, marks: 84 },
  RowDataPacket { name: 'Ross', rollno: 7, marks: 54 },
  RowDataPacket { name: 'Monica', rollno: 8, marks: 86 },
  RowDataPacket { name: 'Lee', rollno: 9, marks: 98 },
  RowDataPacket { name: 'Bruce', rollno: 10, marks: 92 },
  RowDataPacket { name: 'Sukumar', rollno: 11, marks: 99 } ]

NodeJS Example – SELECT from Table with WHERE clause

We shall apply a filter based on marks and fetch only those records with marks greater than 90.

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// include mysql module
var mysql = require('mysql');

// create a connection variable with the required details
var con = mysql.createConnection({
  host: "localhost",	// ip address of server running mysql
  user: "arjun",	// user name to your mysql database
  password: "password",	// corresponding password
  database: "studentsDB" // use the specified database
});

// make to connection to the database.
con.connect(function(err) {
  if (err) throw err;
  // if connection is successful
  con.query("SELECT * FROM students where marks>90", function (err, result, fields) {
	// if any error while executing above query, throw error
    if (err) throw err;
	// if there is no error, you have the result
    console.log(result);
  });
});

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

arjun@arjun-VPCEH26EN:~/workspace/nodejs$ node selectFromWhere.js 
[ RowDataPacket { name: 'Raja', rollno: 5, marks: 94 },
  RowDataPacket { name: 'Lee', rollno: 9, marks: 98 },
  RowDataPacket { name: 'Bruce Wane', rollno: 10, marks: 92 },
  RowDataPacket { name: 'Sukumar', rollno: 11, marks: 99 } ]

NodeJS Example – ORDER entries BY a column

An example to sort entries in ascending order w.r.t a column.

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// include mysql module
var mysql = require('mysql');

// create a connection variable with the required details
var con = mysql.createConnection({
  host: "localhost",	// ip address of server running mysql
  user: "arjun",	// user name to your mysql database
  password: "password",	// corresponding password
  database: "studentsDB" // use the specified database
});

// make to connection to the database.
con.connect(function(err) {
  if (err) throw err;
  // if connection is successful
  con.query("SELECT * FROM students ORDER BY marks", function (err, result, fields) {
	// if any error while executing above query, throw error
    if (err) throw err;
	// if there is no error, you have the result
    console.log(result);
  });
});

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

arjun@arjun-VPCEH26EN:~/workspace/nodejs$ node AscOrderExample.js 
[ RowDataPacket { name: 'Ross', rollno: 7, marks: 54 },
  RowDataPacket { name: 'John', rollno: 1, marks: 74 },
  RowDataPacket { name: 'Arjun', rollno: 2, marks: 74 },
  RowDataPacket { name: 'Prasanth', rollno: 3, marks: 77 },
  RowDataPacket { name: 'Adarsh', rollno: 4, marks: 78 },
  RowDataPacket { name: 'Sai', rollno: 6, marks: 84 },
  RowDataPacket { name: 'Monica Gellar', rollno: 8, marks: 86 },
  RowDataPacket { name: 'Bruce Wane', rollno: 10, marks: 92 },
  RowDataPacket { name: 'Raja', rollno: 5, marks: 94 },
  RowDataPacket { name: 'Lee', rollno: 9, marks: 98 },
  RowDataPacket { name: 'Sukumar', rollno: 11, marks: 99 } ]

The records are sorted in ascending order with respect to marks column.

NodeJS Example – INSERT entries INTO Table

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// include mysql module
var mysql = require('mysql');

// create a connection variable with the required details
var con = mysql.createConnection({
  host: "localhost",	// ip address of server running mysql
  user: "arjun",	// user name to your mysql database
  password: "password",	// corresponding password
  database: "studentsDB" // use the specified database
});

// make to connection to the database.
con.connect(function(err) {
  if (err) throw err;
  // if connection is successful
  con.query("INSERT INTO students (name,rollno,marks) values ('Anisha',12,95)", function (err, result, fields) {
	// if any error while executing above query, throw error
    if (err) throw err;
	// if there is no error, you have the result
    console.log(result);
  });
});

Run above Node.js MySQL program in Terminal.

arjun@arjun-VPCEH26EN:~/workspace/nodejs$ node InsertIntoExample.js 
OkPacket {
  fieldCount: 0,
  affectedRows: 1,
  insertId: 0,
  serverStatus: 2,
  warningCount: 0,
  message: '',
  protocol41: true,
  changedRows: 0 }

Node.js Example – UPDATE Table Entries

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// include mysql module
var mysql = require('mysql');

// create a connection variable with the required details
var con = mysql.createConnection({
  host: "localhost",	// ip address of server running mysql
  user: "arjun",	// user name to your mysql database
  password: "password",	// corresponding password
  database: "studentsDB" // use the specified database
});

// make to connection to the database.
con.connect(function(err) {
  if (err) throw err;
  // if connection is successful
  con.query("UPDATE students SET marks=84 WHERE marks=74", function (err, result, fields) {
	// if any error while executing above query, throw error
    if (err) throw err;
	// if there is no error, you have the result
    console.log(result);
  });
});

Run the above program in Terminal

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 – DELETE Table Entries

Execute DELETE FROM query on specified table with filter applied on one or many properties of records in the table.

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// include mysql module
var mysql = require('mysql');

// create a connection variable with the required details
var con = mysql.createConnection({
  host: "localhost",	// ip address of server running mysql
  user: "arjun",	// user name to your mysql database
  password: "password",	// corresponding password
  database: "studentsDB" // use the specified database
});

// make connection to the database.
con.connect(function(err) {
  if (err) throw err;
  // if connection is successful
  con.query("DELETE FROM students WHERE rollno>10", function (err, result, fields) {
	// if any error while executing above query, throw error
    if (err) throw err;
	// if there is no error, you have the result
    console.log(result);
  });
});

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 Object

We can access the records in Result Set as an array and properties of a record using DOT (.) Operator.

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// Node.js MySQL Result Object Example
// include mysql module
var mysql = require('mysql');
 
// create a connection variable with the required details
var con = mysql.createConnection({
  host: "localhost",    // ip address of server running mysql
  user: "arjun",    // user name to your mysql database
  password: "password",    // corresponding password
  database: "studentsDB" // use the specified database
});
 
// make to connection to the database.
con.connect(function(err) {
  if (err) throw err;
  // if connection is successful
  con.query("SELECT * FROM students", function (err, result, fields) {
    // if any error while executing above query, throw error
    if (err) throw err;
    // if there is no error, you have the result
    // iterate for all the rows in result
    Object.keys(result).forEach(function(key) {
      var row = result[key];
      console.log(row.name)
    });
  });
});

Run the above program using node in Terminal

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

Node.js Example – Parse URL Parameters

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// include 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, action: 'update',id='5221' }
console.log(qdata.type); //returns 'page'
console.log(qdata.action); //returns 'update'
console.log(qdata.id); //returns '5221'

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

Node.js Example – Parse JSON File

Following example helps you to use JSON.parse() function and access the elements from JSON Object.

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// json data
var jsonData = '{"persons":[{"name":"John","city":"New York"},{"name":"Phil","city":"Ohio"}]}';

// parse json
var jsonParsed = JSON.parse(jsonData);

// access elements
console.log(jsonParsed.persons[0].name);

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

Node.js Example – Create HTTP Web Server

Node.js Example – A HTTP Web Server that prepares a response with HTTP header and a message.

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// include http module in the file
var http = require('http');

// create a server
http.createServer(function (req, res) {
	// http header
	// 200 - is the OK message
	// to respond with html content, '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 the response
}).listen(9000); //the server object listens on port 9000

Run the Server

$ node httpWebServer.js

Open a browser and hit the url, “http://127.0.0.1:9000/”, to trigger a request to our Web Server.

TutorialKart

Node.js Examples – Basic Examples, Module Examples, Advanced Examples

Node.js Examples

Node.js Example 1 – Simple Node.js Example

Node.js Example – Create a Module

Node.js Example – Create a File

Node.js Example – Read a File

Node.js Example – Delete a File

Node.js Example – Write to a File

NodeJS Example – Connect to MySQL Database

NodeJS Example – SELECT FROM Table

NodeJS Example – SELECT from Table with WHERE clause

NodeJS Example – ORDER entries BY a column

NodeJS Example – INSERT entries INTO Table

Node.js Example – UPDATE Table Entries

Node.js Example – DELETE Table Entries

Node.js Example – Using Result Object

Node.js Example – Parse URL Parameters

Node.js Example – Parse JSON File

Node.js Example – Create HTTP Web Server

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