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 we shall go through in this Node.js Tutorial :
| Module/Topic | Examples |
| Basics |
|
| File System |
|
| MySQL |
|
| URL |
|
| JSON |
|
| HTTP |
|
Node.js Example : Simple Node.js Example
Following is a simple Node.js Example to print a message to console.
console.log("Hi there! This is Node.js!") |
$ node verifyNode.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.
// 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; }; |
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.
// 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
// 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.
// 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.
// 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
// 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
// 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.
// 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.
// 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
// 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
// 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.
// 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.
// 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
// 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.
// 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.
// 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.
