DEV Community: PRIYA K

Methods in Java

PRIYA K — Tue, 07 Apr 2026 05:40:25 +0000

Methods

Performs a specific task,Improves Readability,Allows code reuse
Can take Parameters and Return a value
Can be Static or Instance
Supports Method Overloading

Basic Syntax

returnType methodName(parameters) {
    // method body
    // code to execute
    return value; // optional
}

Types of Methods in Java
1. Predefined Methods

These are already available in Java libraries.

Example:

System.out.println("Hello");

Here, println() is a predefined method.

2. User-defined Methods

Methods created by the programmer.

Example:

int add(int a, int b) {
    return a + b;
}

- Method Parameters
Methods can accept input values.

void add(int a, int b) {
    System.out.println(a + b);
}

Explanation
a and b are parameters

- Return Type
A method can return a value using return

Example:

int add(int a, int b) {
    return a + b;
}

Usage:
int result = add(5,3);
System.out.println(result);

Output
8

3.Method Without Return Value (void)
If a method does not return anything, we use void.

Example:

void message() {
System.out.println("Welcome");
}

4.Static Methods
Belong to the class,not to the object

class Test {
    static void show() {
        System.out.println("Static Method");
    }

    public static void main(String[] args) {
        show();
    }
}

Hence no object is required

5.Instance Methods
Requires an object to call them

class Test {
    void display() {
        System.out.println("Instance Method");
    }

    public static void main(String[] args) {
        Test t = new Test();
        t.display();
    }
}

6.Method Overloading
Allows multiple methods with the same name but different parameters.

int add(int a, int b){
    return a+b;
}

int add(int a, int b, int c){
    return a+b+c;
}

7.Method can call other methods

void greet(){
    System.out.println("Hello");
}

void welcome(){
    greet();
    System.out.println("Welcome");
}

Types Of Methods

1. Method with No Parameter and No Return Value
No input,does not return anything

class Demo {
    void greet() {
        System.out.println("Hello Priya");
    }

    public static void main(String[] args) {
        Demo d = new Demo();
        d.greet();
    }
}

Output
Hello Priya

Explanation
No Parameter inside ()
No Return Statement
Uses Void

2.Method with Parameter and No Return Value
takes input,does not return anything

class Demo {
    void add(int a, int b) {
        System.out.println(a + b);
    }

    public static void main(String[] args) {
        Demo d = new Demo();
        d.add(5, 3);
    }
}

Output
8

Explanation
Takes parameter a and b
Prints result directly
Uses Void

3.Method with Parameter and Return Value
Takes input and return a value

class Demo {
    int add(int a, int b) {
        return a + b;
    }

    public static void main(String[] args) {
        Demo d = new Demo();
        int result = d.add(5, 3);
        System.out.println(result);
    }
}

Output
8

Explanation
Takes parameter
Returns result using return

4.Method with No Parameter but Return Value
Takes no input , return value

class Demo {
    int number() {
        return 10;
    }

    public static void main(String[] args) {
        Demo d = new Demo();
        int value = d.number();
        System.out.println(value);
    }
}

Output
10

Global Vs Local Variables in Java

PRIYA K — Tue, 07 Apr 2026 04:12:53 +0000

Variables
Named memory location to store data

Example
int age = 20;

TYPES OF VARIABLES
1.Global Variables
2.Local Variables

Simple Memory Concept

Class Area
-----------
Static Variable (1 copy)

Object Area
-----------
Object1 → Instance variables
Object2 → Instance variables

Method Area
-----------
Local variables

Global Variables
Declared inside a class but outside a methods
used by all methods of the class.

class Only_Global
{
    static String name;
    static String breed;
    static int cost;

    public static void main(String args[])
    {
        name = "Scooby";
        breed = "Pug";
        cost = 1000;

        System.out.println(name);
        System.out.println(breed);
        System.out.println(cost);
    }
}

class GlobalExample
{
    String name = "Scooby";  // global variable
    int cost = 1000;         // global variable

    public static void main(String args[])
    {
        GlobalExample d = new GlobalExample();

        System.out.println(d.name);
        System.out.println(d.cost);
    }
}

Types Of Global Variables
1. Instance Variables or NonStatic Variables

Instance variables belong to an object

int id;
String name;

Each object gets separate memory

Student s1 = new Student();
Student s2 = new Student();

Memory Copy depends on object size

new Student()

Object required to call Non-Static Method

s1.display();
s2.display();

Example

class Dog
{
    String breed;   // instance variable

    public static void main(String args[])
    {
        Dog d1 = new Dog();
        Dog d2 = new Dog();

        d1.breed = "Pug";
        d2.breed = "Labrador";

        System.out.println(d1.breed);
        System.out.println(d2.breed);
    }
}

2.Static Variables

Belong to the class

Belong to the class,not to individual objects

class Student {
    static String college = "ABC College";
}

Only one memory copy Only one memory copy is created,no matter how many objects are created.

class Test {
    static int count = 0;
}

All objects share the same value Only one copy, All objects share the same value

class Test {
    static int x = 10;
}

public class Main {
    public static void main(String[] args) {
        Test t1 = new Test();
        Test t2 = new Test();

        t1.x = 50;

        System.out.println(t2.x);
    }
}

Output
50

Explanation
Both objects share the same variable.

Static Variables are declared inside the class Static Variables are declared inside the class,but outside the methods


class Example {
    static int number = 100;
}

Static Variables can be called without creating an object Called using Class name

class Demo {
    static void show() {
        System.out.println("Hello");
    }
}

public class Main {
    public static void main(String[] args) {
        Demo.show();
    }
}

Static methods can access only static variables Cannot directly access Non-Static Variables

class Demo {
    static int a = 10;
    int b = 20;

    static void display() {
        System.out.println(a);
    }
}

Example

class Dog
{
    static String name;

    public static void main(String args[])
    {
        Dog d1 = new Dog();
        Dog d2 = new Dog();

        d1.name = "Scooby";

        System.out.println(d1.name);
        System.out.println(d2.name);
    }
}

Local Variables

- Declared inside a method
Declared inside a method, constructor, or block

class Test {
    void show() {
        int x = 10;  // local variable
        System.out.println(x);
    }

    public static void main(String[] args) {
        Test t = new Test();
        t.show();
    }
}

Output
10

Explanation
Here x is declared inside the method show(), so it is a local variable.

Used only inside that method(Limited Scope)

class Test {
    void display() {
        int num = 5;   // local variable
        System.out.println(num);
    }

    public static void main(String[] args) {
        Test t = new Test();
        t.display();
        // System.out.println(num);  // ERROR
    }
}

Output
Error

Explanation
num works inside display(), but using it in main() causes an error.

Short Lifetime (exists only while method runs)

class Test {
    void count() {
        int a = 20;  // local variable
        System.out.println(a);
    }

    public static void main(String[] args) {
        Test t = new Test();
        t.count();
        t.count();
    }
}

Explanation
Every time count() runs, the variable a is created again and destroyed when the method ends.

Output

20
20

Must be initialised before use

class Test {
    public static void main(String[] args) {
        int x;
        x = 10;     // initialization
        System.out.println(x);
    }
}

Explanation
If we do not assign a value before using x, Java gives an error.

Output
10

No default Value

class Test {
    public static void main(String[] args) {
        int a;
        // System.out.println(a);  // ERROR because not initialized
    }
}

Example

class Only_Local
{
    public static void main(String args[])
    {
        String name = "Scooby";
        String breed = "Pug";
        int cost = 1000;

        System.out.println(name);
        System.out.println(breed);
        System.out.println(cost);
    }
}

Global Variables (not Initialised = Assign Default Values)

class Dog
{
    String name;
    String breed;
    int cost;
}
class Demo
{
    public static void main(String[]args)
    {
        Dog d = new Dog();
        System.out.println(d.name);
        System.out.println(d.breed);
        System.out.println(d.cost);
        d.name = "Scobby";
        d.breed = "Pug";
        d.cost = 10000;
        System.out.println(d.name);
        System.out.println(d.breed);
        System.out.println(d.cost);
    }
}

Sharing Data Between Objects Using Static Variables

class Dog
{
    static String name;
    String breed;
    int cost;
}
class Global_Error
{
    public static void main(String args[])
    {
        Dog d1 = new Dog();
        Dog d2 = new Dog();
        d1.name = "scooby";
        d1.breed = "pug";
        d1.cost = 1000;
        System.out.println(d1.name);
        System.out.println(d2.name);
}
}


//Dog d1 = new Dog();
//Dog d2 = new Dog();

//d1.breed = "Pug";
//d2.breed = "Labrador";

//System.out.println(d1.breed);
//System.out.println(d2.breed);

Using Global Variables Inside Local Variables in Java

class global_inside_local
{
    static String globalName = "Scooby"; // static global variable
    int globalCost = 1000;               // instance global variable

    public static void main(String args[])
    {
        // Local variable using global static variable
        String localName = globalName + " the Dog"; // using static global variable
        System.out.println(localName);

        // Create object to access instance variable
        global_inside_local d = new global_inside_local();

        // Local variable using instance global variable
        int localCost = d.globalCost + 500;        // correct
        System.out.println(localCost);
    }
}

Using Local Variables to Assign Values to Global Variables in Java

class local_inside_global
{
    String name;   // global variable
    int cost;      // global variable

    public static void main(String args[])
    {
        Dog d = new Dog();

        String localName = "Scooby";  // local variable
        int localCost = 1000;         // local variable

        d.name = localName;           // assigning local to global
        d.cost = localCost;

        System.out.println(d.name);
        System.out.println(d.cost);
    }
}

JavaScript Vs Java Vs Python

PRIYA K — Mon, 06 Apr 2026 06:35:01 +0000

What is Python?

Python is a high-level programming language that is simple and easy to understand.
Because its syntax is clear and readable, it is one of the most popular languages for beginners.

Key Features
Easy to learn and read
Dynamically typed (no need to specify data types)
Has many libraries and frameworks available
Interpreted language (runs code line by line)

Common Uses
Data Science and Machine Learning
Artificial Intelligence
Automation and scripting
Web development using frameworks like Django and Flask

What is Java?

Java is a powerful object-oriented programming language mainly used to build large and secure applications.

Key Features
Strongly typed language (data types must be declared)
Platform independent – Write Once, Run Anywhere
Secure and scalable
Runs on the Java Virtual Machine (JVM)

Common Uses
Enterprise applications
Banking and financial software
Android mobile app development
Large backend systems

What is JavaScript?

JavaScript is a programming language used mainly in web development to make websites interactive and dynamic.

Key Features
Runs directly in web browsers
Event-driven and asynchronous
Dynamically typed language
Can be used for both frontend and backend with Node.js

Common Uses
Frontend web development
Interactive website elements (animations, forms)
Real-time apps like chat or live updates
Backend development using Node.js

Programming Language ,Scripting Language

PRIYA K — Mon, 06 Apr 2026 06:32:00 +0000

In software development, the terms programming language and scripting language are sometimes used as if they mean the same thing. But actually, they are a little different in how they run and where they are used.

Programming Language

A programming language is used to create complete software applications.
The code written in these languages is usually compiled first and then executed by the computer.

Main Features
Code must be compiled into machine code
Faster execution speed
Used to build large applications
Gives more control over hardware

Examples
C
C++
Java
Where They Are Used
Operating systems
Desktop software
Game development

Scripting Language

A scripting language is mainly used to automate tasks or control other programs.
These languages usually run line-by-line using an interpreter instead of being compiled first.

Main Features
No separate compilation required
Executed line by line
Generally slower than compiled languages
Easy and quick to write

Examples
Python
JavaScript
PHP

Where They Are Used
Web development
Automation tasks
Backend services

Neon Number,Perfect Number,Strong Number

PRIYA K — Fri, 03 Apr 2026 09:28:33 +0000

1.Neon Number
sum of digits of its square equals the original number.

Example
Number =
Step 1 – Square the number
9 × 9 = 81
Step 2 – Add digits of the square
8 + 1 = 9
Step 3 – Compare with original number
9 = 9
So 9 is a Neon Number.

Steps
1.Take a number n.
2.Calculate square = n × n.
3.Convert the square into digits.
4.Add all digits of the square.
5.Compare the sum with the original number.
6.If equal → Neon Number
If not → Not Neon Number

Python

def neon_no(no):
    sqr = no * no
    res = sqr
    sum = 0

    while res > 0:
        sum = sum + res % 10
        res = res // 10

    if sum == no:
        print("Neon")
    else:
        print("Not Neon")


neon_no(9)

Output

2.Strong Number
Sum of factorial of digits = the number itself
Example

Number = 145
Factorials = 1! + 4! + 5!
= 1 + 24 + 120 = 145

145=1!+4!+5!
145=1+24+120
145=1+24+120
145=145
145=145
So, 145 is a Strong Number.

Steps
Step 1:Take a number from the user.

Step 2:Store the original number in another variable so we can compare later.

Step 3:Extract the last digit using:

digit = n % 10
Step 4:Find the factorial of that digit.

Step 5:Add the factorial to a sum variable.

Step 6:Remove the last digit using:

n = n // 10
Step 7:Repeat the process until the number becomes 0.

Step 8:Compare:

sum == original number
If equal → Strong Number
If not equal → Not Strong Number
Java

import java.util.Scanner;

public class StrongNumber {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        System.out.print("Enter number: ");
        int n = sc.nextInt();

        int temp = n;
        int sum = 0;

        while (n > 0) {
            int digit = n % 10;

            int fact = 1;
            for (int i = 1; i <= digit; i++) {
                fact = fact * i;
            }

            sum = sum + fact;
            n = n / 10;
        }

        if (sum == temp)
            System.out.println("Strong Number");
        else
            System.out.println("Not Strong Number");
    }
}

JavaScript

let n = parseInt(prompt("Enter number:"));
let temp = n;
let sum = 0;

while (n > 0) {
    let digit = n % 10;

    let fact = 1;
    for (let i = 1; i <= digit; i++) {
        fact = fact * i;
    }

    sum = sum + fact;
    n = Math.floor(n / 10);
}

if (sum === temp)
    console.log("Strong Number");
else
    console.log("Not Strong Number");

Python

n = int(input("Enter number: "))
temp = n
sum = 0

while n > 0:
    digit = n % 10

    fact = 1
    for i in range(1, digit + 1):
        fact = fact * i

    sum = sum + fact
    n = n // 10

if sum == temp:
    print("Strong Number")
else:
    print("Not Strong Number")

Output

3.Perfect Number
sum of its proper divisors (factors except the number itself) equals the number.

Example
Factors of 6 (excluding 6 itself):1, 2, 3
Sum of factors:1 + 2 + 3 = 6
Since sum = number, 6 is a Perfect Number.

Steps
1.Take a number n.
2.Find all numbers from 1 to n-1.
3.Check if they divide n exactly.
4.If yes, add them to sum.
5.After the loop, compare:
6.If sum == n → Perfect Number
7.Else → Not Perfect Number

Java

import java.util.Scanner;

public class PerfectNumber {

    static void perfect(int n) {
        int sum = 0;

        for (int i = 1; i < n; i++) {
            if (n % i == 0) {
                sum += i;
            }
        }

        if (sum == n)
            System.out.println("Perfect Number");
        else
            System.out.println("Not a Perfect Number");
    }

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        int n = sc.nextInt();
        perfect(n);
    }
}

JavaScript

function perfect(n) {
    let sum = 0;

    for (let i = 1; i < n; i++) {
        if (n % i === 0) {
            sum += i;
        }
    }

    if (sum === n)
        console.log("Perfect Number");
    else
        console.log("Not a Perfect Number");
}

let n = parseInt(prompt("Enter number:"));
perfect(n);

Python

def perfect(n):
    sum = 0
    for i in range(1,n):
        if n % i == 0:
            sum += i

    if sum == n:
        print("Perfect Number")
    else:
        print("Not a Perfect")

n = int(input())
perfect(n)

def perfect(n):
    sum = 0
    for i in range(1, n):
        if n % i == 0:
            sum += i

    if sum == n:
        return "Perfect Number"
    else:
        return "Not Perfect Number"

n = int(input())
print(perfect(n))

output

javascript questions

PRIYA K — Fri, 05 Dec 2025 00:27:15 +0000

datatypes in Javascript

JavaScript, data types describe the kind of value a variable can hold. JavaScript has two main categories:

🔹 1. Primitive Data Types

Primitive types are simple and immutable.

Number
Represents both integers and decimals.
eg.

let age = 21;
let price = 99.5;

String
Represents text.
eg.

let name = "Priya";

Boolean
Represents true/false values.
eg

let isStudent = true;

Undefined
A variable declared but not assigned a value.
eg

let x;
console.log(x); // undefined

Null
Represents an empty or unknown value.
eg

let data = null;

BigInt
Used for very large numbers beyond Number limit.
eg

let big = 123456789012345678901234567890n;

Symbol
Used for unique values (often in objects).
eg

let id = Symbol("id");

🔹 2. Non-Primitive (Reference) Data Types
These store collections or complex data.

Object
Key–value pairs.
eg

let student = {
  name: "Priya",
  age: 21
};

Array
Ordered list of items (objects but special type).
eg

let colors = ["red", "blue", "green"];

Function
Functions are also objects in JavaScript.
eg

function greet() {
  console.log("Hello!");
}

Types Of Variables in JavaScript

var
Can be redeclared
Can be updated (reassigned)
Has function scope (NOT block scope)
var is old — not recommended now
Example:

var x = 10;
var x = 20; // allowed
x = 30;     // allowed

let
Cannot be redeclared in the same block
Can be updated (reassigned)
Has block scope { }
Preferred for normal variable usage
Example:

let a = 10;
// let a = 20; ❌ not allowed
a = 20;      // ✔ allowed

const
Cannot be redeclared
Cannot be reassigned
Has block scope
Used for values that should NOT change
Example:

const PI = 3.14;
// PI = 3.15; ❌ not allowed

3.Feature Dynamically Typed (JavaScript) Statically Typed (TypeScript, Java)

Type checking Runtime Compile-time
Flexibility High Low
Errors caught While running Before running
Requires type declaration No Yes

Arithmetic Operators

Used for mathematical calculations.

Operator    Meaning
+   Addition
-   Subtraction
*   Multiplication
/   Division
%   Modulus (remainder)
**  Exponent
++  Increment
--  Decrement
 Example:
let a = 10;
let b = 3;

console.log(a + b);  // 13
console.log(a - b);  // 7
console.log(a * b);  // 30
console.log(a / b);  // 3.333
console.log(a % b);  // 1
console.log(a ** b); // 1000
console.log(++a);    // 11
console.log(--b);    // 2

Assignment Operators
Used to assign values.

Operator    Meaning
=   Assign value
+=  Add and assign
-=  Subtract and assign
*=  Multiply and assign
/=  Divide and assign
%=  Modulus and assign
Example:
let x = 10;

x += 5;   // 15
x -= 3;   // 12
x *= 2;   // 24
x /= 4;   // 6
x %= 5;   // 1

Comparison Operators
Used to compare values → returns true/false.

Operator    Meaning
==  Equal to (value only)
=== Strict equal (value + type)
!=  Not equal
!== Strict not equal
>   Greater than
<   Less than
>=  Greater or equal
<=  Less or equal
 Example:
5 == "5";   // true
5 === "5";  // false
10 != 8;    // true
10 !== "10"; // true
10 > 5;     // true
5 < 2;      // false
10 >= 10;   // true
4 <= 5;     // true

Logical Operators
Operator Meaning Example
&& AND → true only if ALL are true true && false → false

! NOT → reverses boolean !true → false

 Example:
true && false; // false
true || false; // true
!true;         // false

Bitwise Operators
Work on binary numbers.
Operator Meaning
& AND

^ XOR
~ NOT
<< Left shift( a * 2^ b)

Right shift( a / 2^ b)

Unsigned right shift

Example:
5 & 1;  // 1
5 | 1;  // 5
5 ^ 1;  // 4
~5;     // -6
5 << 1; // 10
5 >> 1; // 2

Ternary Operator
Short form of if-else.
Syntax:
condition ? valueIfTrue : valueIfFalse

Example:
let age = 20;
let result = age >= 18 ? "Adult" : "Minor";
console.log(result); // Adult

IF Statement in JavaScript
The if statement is used to run a block of code only if a condition is true.
Syntax:

if (condition) {
    // code to run
}

Example 1: Basic if

let age = 20;

if (age >= 18) {
    console.log("You are eligible to vote");
}

Output:
You are eligible to vote

IF–ELSE Statement

If the condition is true → one block runs
If false → another block runs

✔ Example 2: if–else

let mark = 45;

if (mark >= 50) {
    console.log("Pass");
} else {
    console.log("Fail");
}

Output:

Fail

ELSE IF Statement

Used when there are multiple conditions.

✔ Example 3: if–else if–else

let temp = 32;

if (temp > 35) {
    console.log("Hot");
} else if (temp > 20) {
    console.log("Warm");
} else {
    console.log("Cold");
}

Output:

✅ Nested IF Statement

A nested if means:
👉 An if statement inside another if.

➤ Used when one condition depends on another.
✔ Example 4: Nested if

let username = "Priya";
let password = "12345";

if (username === "Priya") {    // Outer if
    if (password === "12345") {   // Nested (inner) if
        console.log("Login Successful");
    } else {
        console.log("Incorrect Password");
    }
} else {
    console.log("User not found");
}

Output:

Conditional (Ternary) Operator

The ternary operator is a shorthand way of writing an if…else statement.

✔ Syntax
condition ? value_if_true : value_if_false;

✔ Example 1: Check age

let age = 20;
let result = (age >= 18) ? "Adult" : "Minor";

console.log(result); // Output: Adult

✔ Example 2: Even or Odd

let num = 7;
let type = (num % 2 === 0) ? "Even" : "Odd";

console.log(type);   // Output: Odd

Ternary operator with more than one condition

You can nest ternary operators (but not recommended if too long):

let marks = 85;

let grade = (marks >= 90) ? "A+" :
            (marks >= 75) ? "A" :
            (marks >= 50) ? "B" : "Fail";

console.log(grade); 
// Output: A

switch Statement

The switch statement checks one value against multiple possible cases.

✔ Syntax

switch(value) {
    case option1:
        // code
        break;

    case option2:
        // code
        break;

    default:
        // code if no case matches
}

✔ Example: Day of the Week

let day = 3;

switch(day) {
    case 1:
        console.log("Monday");
        break;
    case 2:
        console.log("Tuesday");
        break;
    case 3:
        console.log("Wednesday");
        break;
    case 4:
        console.log("Thursday");
        break;
    default:
        console.log("Invalid day");
}

Output:

Wednesday

✔ Example: Calculator Using Switch

let a = 10;
let b = 5;
let operator = "+"; 

switch(operator) {

    case "+":
        console.log(a + b);
        break;

    case "-":
        console.log(a - b);
        break;

    case "*":
        console.log(a * b);
        break;

    case "/":
        console.log(a / b);
        break;

    default:
        console.log("Invalid operator");
}

Output:

The break Keyword

The break statement stops the execution of a switch case.

let fruit = "apple";

switch (fruit) {
    case "apple":
        console.log("Apple selected");
        break;  // stops here

    case "banana":
        console.log("Banana selected");
        break;

    case "orange":
        console.log("Orange selected");
        break;
}

Output:

Apple selected

The default Keyword

default runs when no cases match.

✔ Example:

let color = "purple";

switch(color) {
    case "red":
        console.log("Red Color");
        break;

    case "blue":
        console.log("Blue Color");
        break;

    default:
        console.log("No matching color found");
}

Output:

No matching color found

Strict Comparison (=== and !==)

Strict comparison checks both value AND data type.

✔ === → Strict Equal
✔ !== → Strict Not Equal
🔍 Strict Comparison Examples
✔ Example 1: === Checks value + type
console.log(5 === 5); // true
console.log(5 === "5"); // false (number vs string)

✔ Example 2: !== Checks value + type
console.log(10 !== 10); // false
console.log(10 !== "10"); // true (type different)

🔥 Strict vs Loose Comparison

Loose comparison (==) only checks value, not type.

console.log(5 == "5"); // true (only value checked)
console.log(5 === "5"); // false (type different)

⭐ Full Combined Example
let value = "10";

switch(value) {
case 10: // number
console.log("Number 10");
break;

case "10":                    // string
    console.log("String 10");
    break;

default:
    console.log("No match");

}

// Strict comparison:
console.log(value === 10); // false
console.log(value === "10"); // true
console.log(value !== 10); // true

Output:

String 10
false
true
true

Boolean in JavaScript

A Boolean represents true or false.

✔ Example:

let isLoggedIn = true;
let isAdult = false;

console.log(isLoggedIn); // true
console.log(isAdult);    // false

Booleans as Objects

You can create a Boolean object using new Boolean().

⚠️ Avoid using Boolean objects — they behave differently.

✔ Example:

let x = false;               // boolean primitive
let y = new Boolean(false);  // boolean object

console.log(typeof x); // "boolean"
console.log(typeof y); // "object"

for Loop

Used when you know how many times to run the loop.

✔ Example:

for (let i = 1; i <= 5; i++) {
    console.log("Number:", i);
}

Output:
1
2
3
4
5

while Loop

Used when you want to run the loop until a condition becomes false.

✔ Example:

let i = 1;

while (i <= 5) {
    console.log("Count:", i);
    i++;
}

for…in Loop

Used to iterate over object properties (keys).

✔ Example:
let person = {
name: "Priya",
age: 21,
city: "Chennai"
};

for (let key in person) {
console.log(key, ":", person[key]);
}

Output:
name : Priya
age : 21
city : Chennai

for…of Loop

Used to iterate over values of arrays, strings, etc.

✔ Example (Array):
let numbers = [10, 20, 30];

for (let value of numbers) {
console.log(value);
}

Output:
10
20
30

Logical AND (&&)
✔ Works when both conditions must be TRUE

let age = 20;
let hasID = true;

if (age >= 18 && hasID) {
console.log("You can enter.");
}

Logical OR (||)
✔ Works when at least one condition is TRUE
Example (conditions):
let isAdmin = false;
let isUser = true;

if (isAdmin || isUser) {
console.log("Access granted.");
}
. Logical NOT (!)
✔ Converts truthy → false
✔ Converts falsy → true
✔ Example:
console.log(!true); // false
console.log(!false); // true
console.log(!0); // true (0 is falsy)
console.log(!"Priya"); // false (string is truthy)

Nullish Coalescing Operator (??)

✔ Returns the right-side value only if left side is null or undefined
✔ Does NOT treat 0, "", false as null

✔ Examples:
let a = null;
console.log(a ?? "Default"); // "Default"

let b = undefined;
console.log(b ?? "Value Missing"); // "Value Missing"

let c = 0;
console.log(c ?? 100); // 0 (because 0 is NOT null/undefined)

let d = "";
console.log(d ?? "Empty"); // "" (string is not null/undefined)

JavaScript Loops

Loops allow you to repeat a block of code multiple times.

Common Loops in JS:

for

while

do...while

for...in

for...of

Loop Scope

A variable declared inside a loop (with let or const) is accessible only inside that loop block.

Example (var leaks outside):
for (var i = 1; i <= 3; i++) {
}
console.log(i); // ✔ i is accessible (var is not block scoped)
The While Loop

Runs as long as the condition is TRUE.

✔ Example:
let n = 1;

while (n <= 5) {
console.log("While Loop:", n);
n++;
}

The Do…While Loop

✔ Runs the code at least once, even if the condition is false.
✔ Condition is checked after the loop body.

✔ Example:
let x = 1;

do {
console.log("Do While Loop:", x);
x++;
} while (x <= 5);

The For Loop

Use a for loop when you know how many times you want to repeat something.

✔ Syntax:
for (initialization; condition; increment) {
// code block
}

✔ Example:
for (let i = 1; i <= 5; i++) {
console.log("For Loop:", i);
}

Output:
1
2
3
4
5

Comparing For and While Loops
Feature For Loop While Loop
Best Used When Number of iterations is known Number of iterations unknown
Structure All parts (init, condition, increment) in one line Parts written separately
Readability More compact More flexible
Risk Less chance of infinite loop More chance of forgetting increment (infinite loop)

Break in Loops

The break statement stops the loop immediately.

✔ Example – break inside a for loop
for (let i = 1; i <= 5; i++) {
if (i === 3) {
break; // stops the loop when i = 3
}
console.log(i);
}

Output:

1
2

Break in a Switch Statement

break is used to stop execution of other cases.

✔ Example:
let color = "blue";

switch (color) {
case "red":
console.log("Red");
break;

case "blue":
    console.log("Blue");
    break; // stops here

case "green":
    console.log("Green");
    break;

default:
    console.log("No match");

}

Output:

Blue

JavaScript Labels

A label is a name placed before a block of code.
It is used with break to exit from nested loops.

✔ Syntax:
labelName: {
// statements
}

✔ Best Use: Breaking out of nested loops
✔ Example – break with label
outerLoop: for (let i = 1; i <= 3; i++) {
for (let j = 1; j <= 3; j++) {

    if (i === 2 && j === 2) {
        break outerLoop; // exits both loops
    }

    console.log(i, j);
}

}

Output:

1 1
1 2
1 3
2 1

JavaScript Continue

continue skips the current iteration and moves to the next iteration of the loop.

✔ Example:
for (let i = 1; i <= 5; i++) {
if (i === 3) {
continue; // skip 3
}
console.log(i);
}

Output:

1
2
4
5

The number 3 is skipped.
Continue to Label (Labeled Continue)

continue labelName jumps directly to the next iteration of the labeled loop, skipping everything below it.

✔ Example (Skip inner loop and continue outer loop)
outerLoop: for (let i = 1; i <= 3; i++) {

for (let j = 1; j <= 3; j++) {
    if (j === 2) {
        continue outerLoop;  
        // skips inner loop and jumps to next 'i'
    }
    console.log(i, j);
}

}

Output:

1 1
2 1
3 1

JavaScript Strings

A string is text inside quotes:

" " (double quotes)

' ' (single quotes)

(backticks — template strings)

✔ Example:
let name = "Priya";
let city = 'Chennai';
console.log(name, city);

String Length

.length returns the number of characters.

✔ Example:
let text = "JavaScript";
console.log(text.length); // 10

Escape Characters

Used to insert special characters inside strings.

Escape Meaning
\" Double quote
\' Single quote
\ Backslash
\n New line
\t Tab
\r Carriage return
✔ Examples:
let str1 = "She said, \"Hello!\"";
let str2 = 'It\'s a nice day';
let str3 = "Line1\nLine2"; // new line
let str4 = "Tab:\tSpace";

output
console.log(str1);
console.log(str2);
console.log(str3);
console.log(str4);

JavaScript Strings as Objects

You can create a string object using new String().

✔ Example:
let str1 = "Hello"; // string primitive
let str2 = new String("Hello"); // string object

console.log(typeof str1); // "string"
console.log(typeof str2); // "object"

String Methods

Javascript strings are primitive and immutable: All string methods produce a new string without altering the original string.

String length

Returns the number of characters in a string.

let text = "Hello World";
console.log(text.length); // 11

String charAt()

Returns the character at a specified index.

let text = "Hello";
console.log(text.charAt(1)); // e

String charCodeAt()

Returns UTF-16 code (0–65535) of the character at an index.

let text = "A";
console.log(text.charCodeAt(0)); // 65

String codePointAt()

Returns Unicode code point (works for emojis also).

let emoji = "😀";
console.log(emoji.codePointAt(0)); // 128512

String concat()

Joins two or more strings.

let a = "Hello";
let b = "World";
console.log(a.concat(" ", b)); // Hello World

String at()

Returns the character at a position (supports negative index).

let text = "Hello";
console.log(text.at(-1)); // o

String

Access a character like an array.

let text = "Hello";
console.log(text[0]); // H

String slice()

Extracts part of a string.

let text = "JavaScript";
console.log(text.slice(0, 4)); // Java
console.log(text.slice(-6)); // Script

String substring()

Similar to slice(), but does NOT support negative values.

let text = "JavaScript";
console.log(text.substring(4, 10)); // Script

String substr() (❌ Deprecated but still works)

Extracts a substring with start index and length.

let text = "JavaScript";
console.log(text.substr(4, 6)); // Script

String toUpperCase()

Converts to uppercase.

let text = "hello";
console.log(text.toUpperCase()); // HELLO

String toLowerCase()

Converts to lowercase.

let text = "HELLO";
console.log(text.toLowerCase()); // hello

String isWellFormed()

Checks if string contains only valid Unicode characters.

console.log("hello".isWellFormed()); // true

String toWellFormed()

Replaces invalid Unicode with valid ones.

console.log("\uD800".toWellFormed()); // �

String trim()

Removes whitespace from both ends.

let text = " hi ";
console.log(text.trim()); // "hi"

String trimStart() / trimLeft()

Removes whitespace from start.

let text = " Hi";
console.log(text.trimStart()); // "Hi"

String trimEnd() / trimRight()

Removes whitespace from end.

let text = "Hi ";
console.log(text.trimEnd()); // "Hi"

String padStart()

Pads a string at the beginning.

let num = "5";
console.log(num.padStart(4, "0")); // 0005

String padEnd()

Pads a string at the end.

let num = "5";
console.log(num.padEnd(4, "")); // 5**

String repeat()

Repeats the string.

console.log("ha".repeat(3)); // hahaha

String replace()

Replaces first occurrence.

let text = "I love JavaScript";
console.log(text.replace("JavaScript", "Python"));
// I love Python

String replaceAll()

Replaces all occurrences.

let text = "apple apple apple";
console.log(text.replaceAll("apple", "orange"));
// orange orange orange

String split()

Splits a string into an array.

let text = "a,b,c";
console.log(text.split(",")); // ["a", "b", "c"]

JavaScript String Search Methods (with Examples)

These methods help you find text inside a string.

✅ 1. String indexOf()

Returns the first index of a substring.
Returns -1 if not found.

let text = "Hello JavaScript";

console.log(text.indexOf("Java")); // 6
console.log(text.indexOf("hello")); // -1 (case-sensitive)

✅ 2. String lastIndexOf()

Returns the last index of a substring.

let text = "Hello JavaScript Java";

console.log(text.lastIndexOf("Java")); // 17

✅ 3. String search()

Searches for a substring or regular expression.

let text = "I love JavaScript";

console.log(text.search("love")); // 2
console.log(text.search(/Java/i)); // 7 (regex, case-insensitive)

✅ 4. String match()

Returns matches of a regex as an array.

let text = "cat, bat, mat";

console.log(text.match(/at/g)); // ["at", "at", "at"]

✅ 5. String matchAll()

Returns all matches including details (iterator).

let text = "cat, bat, mat";

for (let m of text.matchAll(/at/g)) {
console.log(m);
}

Output will be:

["at", index: 1]
["at", index: 6]
["at", index: 11]

✅ 6. String includes()

Checks if a string contains another string.
Returns true/false.

let text = "Hello World";

console.log(text.includes("World")); // true
console.log(text.includes("world")); // false

✅ 7. String startsWith()

Checks if string begins with a substring.

let text = "JavaScript is fun";

console.log(text.startsWith("Java")); // true
console.log(text.startsWith("Script")); // false

✅ 8. String endsWith()

Checks if string ends with a substring.

let text = "Hello World";

console.log(text.endsWith("World")); // true
console.log(text.endsWith("Hello")); // false

JavaScript Number – Basic Methods

In JavaScript, numbers are usually primitive values, but JS automatically treats them as Number objects when you use methods.

let num = 123;

✅ 1. toString()
📌 Definition

Converts a number to a string.

✅ Example
let num = 100;
console.log(num.toString()); // "100"
console.log(typeof num.toString()); // string

👉 You can also convert to different bases:

let n = 15;
console.log(n.toString(2)); // "1111" (binary)
console.log(n.toString(8)); // "17" (octal)
console.log(n.toString(16)); // "f" (hex)

toExponential() 📌 Definition

Returns a number written in exponential (scientific) notation.

✅ Example
let num = 12345;
console.log(num.toExponential()); // "1.2345e+4"

With decimal places:

let n = 9.656;
console.log(n.toExponential(2)); // "9.66e+0"

📌 Mostly used in scientific and large number calculations.

toFixed() 📌 Definition

Formats a number with a fixed number of decimal places.
Returns a string.

✅ Example
let num = 4.56789;
console.log(num.toFixed(2)); // "4.57"
console.log(num.toFixed(0)); // "5"

✅ Very common in currency & billing apps.

toPrecision() 📌 Definition

Formats a number to a specified total number of digits.

✅ Example
let num = 123.456;
console.log(num.toPrecision(4)); // "123.5"
console.log(num.toPrecision(2)); // "1.2e+2"

📌 Includes both integer + decimals.

valueOf() 📌 Definition

Returns the primitive value of a Number object.

✅ Example
let num = new Number(100);

console.log(num.valueOf()); // 100
console.log(typeof num); // object
console.log(typeof num.valueOf()); // number

✅ JavaScript usually calls valueOf() automatically.

JavaScript Number – Static Methods

📌 Important:
Static methods can only be used on Number, not on number variables.

✅ Correct: Number.isInteger(10)

Number.isFinite() 📖 Definition

Checks whether a value is a finite number.
Returns true only for real numbers (not Infinity, -Infinity, or NaN).

✅ Example
console.log(Number.isFinite(100)); // true
console.log(Number.isFinite(Infinity)); // false
console.log(Number.isFinite(NaN)); // false
console.log(Number.isFinite("100")); // false

Number.isInteger() 📖 Definition

Checks whether a value is an integer.

✅ Example
console.log(Number.isInteger(10)); // true
console.log(Number.isInteger(10.5)); // false
console.log(Number.isInteger("10")); // false

✅ 3. Number.isNaN()
📖 Definition

Checks whether a value is exactly NaN.
Better and safer than global isNaN().

✅ Example
console.log(Number.isNaN(NaN)); // true
console.log(Number.isNaN(10)); // false
console.log(Number.isNaN("Hello")); // false

Number.isSafeInteger() 📖 Definition

Checks whether a number is a safe integer
(i.e., between −(2⁵³ − 1) and (2⁵³ − 1)).

✅ Example
console.log(Number.isSafeInteger(1000)); // true
console.log(Number.isSafeInteger(9007199254740991)); // true
console.log(Number.isSafeInteger(9007199254740992)); // false

📌 Used in banking & large calculations.

Number.parseInt() 📖 Definition

Parses a value and returns an integer.
Ignores decimals.

✅ Example
console.log(Number.parseInt("100")); // 100
console.log(Number.parseInt("100.75")); // 100
console.log(Number.parseInt("10 years")); // 10

Number.parseFloat() 📖 Definition

Parses a value and returns a floating-point number.

✅ Example
console.log(Number.parseFloat("10.55")); // 10.55
console.log(Number.parseFloat("10.55px")); // 10.55
console.log(Number.parseFloat("10")); // 10

JavaScript Number Properties

📌 Important:
Number properties are static, so they are accessed using Number.
✅ Number.MAX_VALUE
❌ num.MAX_VALUE

✅ 1. Number.EPSILON
📖 Definition

The smallest difference between 1 and the next larger floating-point number.

Used to compare decimal numbers safely.

✅ Example
let a = 0.1 + 0.2;
let b = 0.3;

console.log(a === b); // false

console.log(Math.abs(a - b) < Number.EPSILON); // true

✅ 2. Number.MAX_VALUE
📖 Definition

The largest number JavaScript can safely represent.

✅ Example
console.log(Number.MAX_VALUE);
// 1.7976931348623157e+308

console.log(Number.MAX_VALUE * 2); // Infinity

✅ 3. Number.MIN_VALUE
📖 Definition

The smallest positive number greater than 0.

✅ Example
console.log(Number.MIN_VALUE);
// 5e-324

⚠️ Not the most negative number!

✅ 4. Number.MAX_SAFE_INTEGER
📖 Definition

The largest safe integer JavaScript can accurately represent.

✅ Example
console.log(Number.MAX_SAFE_INTEGER);
// 9007199254740991

console.log(Number.isSafeInteger(Number.MAX_SAFE_INTEGER)); // true

✅ 5. Number.MIN_SAFE_INTEGER
📖 Definition

The smallest safe integer JavaScript can represent.

✅ Example
console.log(Number.MIN_SAFE_INTEGER);
// -9007199254740991

✅ 6. Number.POSITIVE_INFINITY
📖 Definition

Represents positive infinity.

✅ Example
console.log(Number.POSITIVE_INFINITY); // Infinity
console.log(1 / 0); // Infinity

✅ 7. Number.NEGATIVE_INFINITY
📖 Definition

Represents negative infinity.

✅ Example
console.log(Number.NEGATIVE_INFINITY); // -Infinity
console.log(-1 / 0); // -Infinity

✅ 8. Number.NaN
📖 Definition

Represents Not-a-Number.

✅ Example
console.log(Number.NaN); // NaN
console.log(0 / 0); // NaN
console.log(Number("hello")); // NaN

✅ Check NaN correctly:

console.log(Number.isNaN(Number.NaN)); // true

What are Functions?
Functions are fundamental building blocks in all programming.
Functions are reusable block of code designed to perform a particular task.
Functions are executed when they are "called"

JavaScript Function Syntax
function name( p1, p2, ... ) {
// code to be executed
}

Functions are defined with the function keyword:
followed by the function name
followed by parentheses ( )
followed by brackets { }
The function name follows the naming rules for variables.
Optional parameters are listed inside parentheses: ( p1, p2, ... )
Code to be executed is listed inside curly brackets: { }
Functions can return an optional value back to the caller.

Function Invocation ()
The code inside the function will execute when "something" invokes (calls) the function:
When it is invoked (called) from JavaScript code
When an event occurs (a user clicks a button)
Automatically (self invoked)
The () operator invokes a the function.

Normal (Named) Function
Definition
A normal function is declared using the function keyword and has a name.
Example 1

function greet() {
    console.log("Hello World");
}
greet(); // function call

output
Hello World

Example 2
console.log('outside');
function makeBiryani(){
console.log("biryani");
}
output:
outside

Example 3
console.log('outside');
function makeBiryani(){
console.log("biryani");
}
makeBiryani();
output:
outside
biryani

Function with Parameters
Definition
Parameters allow you to pass values into a function.

Example 1
function add(a, b) {
    console.log(a + b);
}
add(10, 20);
output
30

Example 2
console.log('outside');
        function makeBiryani(rice_container , masala_box){
            console.log("biryani");
            console.log(rice_container);
            console.log(masala_box);
        }
        makeBiryani("SeeragaSamba")
        makeBiryani("Aachi")

output 
outside
biryani
seeragasamba
undefined
outside
biryani
Aachi
undefined

Example 3
console.log('outside');
        function makeBiryani(rice_container , masala_box){
            console.log("biryani");
            console.log(rice_container);
            console.log(masala_box);
        }
        makeBiryani("SeeragaSamba")

output
outside
biryani
seeragasamba
undefined

Example 4
console.log("outside")
        function makeBiryani(rice_container , masala_box){
            console.log("biryani")
            console.log(rice_container)
            console.log(masala_box)
        }
        makeBiryani("SeeragaSamba","Aachi")

output
outside
biryani
seeragasamba
Aachi

Example 5
console.log("outside")
        function makeBiryani(rice_container , masala_box){
            console.log("biryani")           
        }
        makeBiryani("SeeragaSamba","Aachi")
output
outside
biryani

Example 6

Function with Return Value
Definition
A function can return a value using the return keyword.

Example
function multiply(x, y) {
    return x * y;
}
let result = multiply(5, 4);
console.log(result);

What is Scope in JavaScript?
Scope defines where a variable can be accessed in a program.
There are mainly two important scopes:
Global Scope
Local Scope
first priority is given to local scope.

Global Scope
Definition
A variable declared outside any function or block is in the global scope.
It can be accessed from anywhere in the program.
Lifetime: Entire program
Memory: Occupies memory longer

Example
let message = "Hello World"; // Global variable
function showMessage() {
console.log(message);
}
showMessage();
console.log(message);

Output
Hello World
Hello World
//Accessible inside and outside functions

Local Scope
Definition
A variable declared inside a function or block is in the local scope.
It can be accessed only inside that function or block.
Lifetime: Until function/block ends
Memory: Freed after execution
Function Scope (Local Scope)
function cooking() {
let food = "Biryani"; // local variable
console.log(food);
}

cooking();
console.log(food); // ❌ Error

Error
ReferenceError: food is not defined

example 1
let product = "biscuit"
console.log(product)
buymilk()
function buymilk(){
let product = "milk"
console.log("inside function",product)
}

output
biscuit
inside function milk

example 2
let product = "biscuit"
console.log(product)
buymilk()
function buymilk(){
console.log("inside function",product)
}

output
biscuit
inside function biscuit

Parameters vs. Arguments
Parameters are the names listed in the function definition.
Arguments are the values received by the function.
Examples
"name" and "age" are parameters:
function greet(name, age) {
return Hello ${name}! You are ${age} years old.;
}

"John" and 21 are arguments:
greet("John", 21);

Function Parameters and Arguments
syntax:
function functionName(parameter1, parameter2, parameter3) {
// code to be executed
}

Parameter Rules
JavaScript function definitions do not specify data types for parameters.
JavaScript functions do not perform type checking on the passed arguments.
JavaScript functions do not check the number of arguments received.

Default parameter
Rest parameter
Return
One function using return statement for giving input for another function

example 1
function buyMilk(){
return "milk";
}
let container = buyMilk();
console.log(container)

output
milk

example 2
function buyMilk(){
return "milk";
console.log("milk");
}
let container = buyMilk();
console.log(container);

output
unreachable code after return statement
milk

example 3
function buyMilk(){
console.log("milk");
return "milk";
}
let container = buyMilk();
console.log(container);

output
milk
milk

example 4
function buymilk(){
let product = "milk";
return product;
}
let product = buymilk();
console.log(product);

output
milk

example 5
function buymilk(){
let product = "milk";
return product;
}
let product = buymilk();
console.log(product);
output
milk

example 6
let product = "biscuit"
console.log(product)
buymilk()
function buymilk(){
let product = "milk"
console.log("inside function",product)
}

output
biscuit
inside function milk

example 7
buymilk();
buybiscuit();
function buymilk(){
let product = "biscuit"
console.log("inside milk",product)
}
function biscuit(){
console.log("inside",product)
}
output
inside milk biscuit

example 8
buymilk();
buybiscuit();
function buymilk(){
let product = "biscuit"
console.log("inside",product)
}
function buybiscuit(){
console.log("inside",product)
}
output
inside biscuit
error(product is not defined)

Return
example 1
function add(){
let i = 10;
let j = 20;
return i,j;
}
output
error

example 2
function add(){
let i = 10;
let j = 20;
return 10,20;
}
output
error

example 3
function add(){
let i = 10;
let j = 20;
return i + j;
}
output
30

convert function into function expression by
not using function names

What is a Function Expression?
A function expression is a function assigned to a variable.
A function expression is a way of defining a function within an expression, rather than as a standalone declaration.
A function expression can be assigned to a variable, passed as an argument to another function, or returned from a function.
Example
const x = function (a, b) {return a * b};

example
const x = function (a, b) {return a * b};
let z = x(4, 3);
output
12
The function above is actually an anonymous function (a function without a name).

Functions stored in variables do not need function names. They are always invoked (called) using the variable name

Function Declarations
A function declaration (or simply a function) is defined using the function keyword followed by a function name, parameters, and a code block:
function add(a, b) {return a + b;}

Function Expressions
A function expression is defined by assigning an anonymous function to a variable:
const add = function(a, b) {return a + b;};
Note
Function expressions are commonly used to create anonymous functions.
Anonymous functions are functions without a name.
Function declarations are "hoisted" to the top of their scope. This means you can call a function before it is defined in the code:
let sum = add(2, 3);
function add(a, b) {return a + b;}

Semicolons are used to separate executable JavaScript statements.
Since a function declaration is not an executable statement, it is not common to end it with a semicolon.

let sum = add(2, 3); // ⛔ Will generate error.
const add = function (a, b) {return a + b;};

Arrow Functions allow a shorter syntax for function expressions.

You ca skip the function keyword, the return keyword, and the curly brackets:
let myFunction = (a, b) => a * b;
Before Arrow:

Function to compute the product of a and b
let myFunction = function(a, b) {return a * b}

With Arrow
let myFunction = (a, b) => a * b;

Before Arrow:
let hello = function() {
return "Hello World!";
}

With Arrow Function:
let hello = () => {
return "Hello World!";
}

If the function has only one statement that returns a value, you can remove the brackets and the return keyword:
Arrow Functions Return Value by Default:
let hello = () => "Hello World!";

Arrow functions must be defined before they are used.

You can only omit the return keyword and the curly brackets if the function is a single statement. Because of this, it might be a good habit to always keep them:
Example
// This will not work
let myFunction = (x, y) => { x * y } ;

// This will not work
let myFunction = (x, y) => return x * y ;

// Only this will work
let myFunction = (x, y) => { return x * y };

object

An Object is a variable that can hold many variables.
object inside functions are methods.
object is the combination of states and behaviour.
object contains information and methods.
information(Attributes,properties,states)
new object() is not neccessary

eg
const person ={}; (object)

JavaScript Objects
What is a JavaScript Object?
A JavaScript object is a collection of key–value pairs.
Keys are called properties, and values can be data or functions (methods).

🔹 Definition:

An object stores related data and functionality together.

🔹 Example:
let student = {
name: "Priya",
age: 21,
course: "AI & DS"
};

Note:

You should declare objects with the const keyword.
When an object is declared with const, you cannot later reassign it to point to a different variable.
It does not make the object unchangeable. You can still modify its properties and values.

🛠 How to Create a JavaScript Object

inside curly braces { }:
1️⃣ Using Object Literal (Most Common Method)
Syntax:
let objectName = {
property1: value1,
property2: value2
};

Example:
let car = {
brand: "Toyota",
model: "Innova",
year: 2023
};

console.log(car.brand); //
output
Toyota

2️⃣ Using the new Object() Method
Syntax:
let objectName = new Object();

new keyword calls the constructor
Example:
let person = new Object();
person.name = "Rahul";
person.age = 25;
person.city = "Chennai";

console.log(person);

output
Object { name: "Rahul", age: 25, city: "Chennai" }
There is no need to use new Object()
Object Properties

You can access object properties in two ways:
objectName.propertyName
objectName["propertyName"]

JavaScript Object Methods
Object methods are actions that can be performed on objects.
Object methods are function definitions stored as property values:
Sometimes we need to create many objects of the same type.
To create an object type we use an object constructor function.

object Constructor Function
Definition:
A constructor function is used to create multiple objects of the same type.
Syntax:
function Person(name, age) {
this.name = name;
this.age = age;
}
Example:
function Student(name, rollNo, department) {
this.name = name;
this.rollNo = rollNo;
this.department = department;
}

let s1 = new Student("Priya", 101, "AI & DS");
let s2 = new Student("Arun", 102, "CSE");

console.log(s1.name); // Priya

Note:
In the constructor function, this has no value.
this = refers to current object.
this = works only inside function
The value of this will become the new object when a new object is created.
Constructor function starts with the capital letters.
constructor is called automatically when the object is created
constructor = assigning object specific values into variables

Objects are containers for Properties and Methods.
Properties are named Values.
Methods are Functions stored as Properties.
Properties can be primitive values, functions, or even other objects.
Constructors are Object Prototypes.

example
constructor function
const myFather = new Person("John", "Doe", 50, "blue");
const myMother = new Person("Sally", "Rally", 48, "green");
const mySister = new Person("Anna", "Rally", 18, "green");
const mySelf = new Person("Johnny", "Rally", 22, "green");

    function Person(first,last,age,eyecolor){
        this.firstname = first,
        this.lastname = last,
        this.age = age,
        this.eyecolor = eyecolor;
    }
    console.log(myFather.eyecolor);

output
blue

constructor function
const myFather = new Person("John", "Doe", 50);
const myMother = new Person("Sally", "Rally", 48, "green");
const mySister = new Person("Anna", "Rally", 18, "green");
const mySelf = new Person("Johnny", "Rally", 22, "green");

    function Person(first,last,age,eyecolor){
        this.firstname = first,
        this.lastname = last,
        this.age = age,
        this.eyecolor = eyecolor;
    }
    console.log(myFather.eyecolor);

output
undefined

Object Properties in JavaScript
🔹 Accessing Object Properties
1️⃣ Dot Notation
console.log(student.name);

2️⃣ Bracket Notation
console.log(student["age"]);

📌 Use bracket notation when:

Property name has spaces

Property name is stored in a variable

Example:
let key = "course";
console.log(student[key]);

🔹 Adding New Properties
student.grade = "A";

🔹 Updating Properties
student.age = 22;

🔹 Deleting Properties
delete student.course;

🔹 Object with Methods
Example:
let user = {
name: "Priya",
login: function () {
console.log("User logged in");
}
};

user.login();

🔍 Check Property Exists
Using in operator:
console.log("name" in user); // true

🔁 Loop Through Object Properties
Using for...in loop:
for (let key in student) {
console.log(key + ": " + student[key]);
}

What are Object Methods?
When a function is stored inside an object, it is called a method.

🔸 Example:
let user = {
name: "Priya",
age: 21,
greet: function () {
console.log("Hello, " + this.name);
}
};
user.greet();

📌 Output:
Hello, Priya
✔ this refers to the current object

JavaScript Object Properties
An Object is an Unordered Collection of Properties
Properties are the most important part of JavaScript objects.
Properties can be changed, added, deleted, and some are read only.
Accessing JavaScript Properties

The syntax for accessing the property of an object is:
// objectName.property
let age = person.age;

or
//objectName["property"]
let age = person["age"];

or
//objectName[expression]
let age = person[x];
Examples
person.firstname + " is " + person.age + " years old.";
person["firstname"] + " is " + person["age"] + " years old.";
let x = "firstname";
let y = "age";
person[x] + " is " + person[y] + " years old.";

Adding new attributes:
eg
const person = {
name: "Priya",
age: 23
};
person.city = "Chennai";
console.log(person);
output
Object { name: "Priya", age: 23, city: "Chennai" }

update:
just assign a new value to the same key
eg
const person = {
name: "Priya",
age: 23,
city : "Chennai"
};
person.city = "london";
console.log(person.city);
output
london

delete:
the delete keyword deletes a property from an object
eg
const person = {
name: "Priya",
age: 23,
city : "Chennai"
};
delete person.city;
console.log(person);
output
Object { name: "Priya", age: 23 }

The delete keyword deletes both the value of the property and the property itself.
After deletion, the property cannot be used before it is added back again.

JavaScript Object Methods:
Object methods are actions that can be performed on objects.
A method is a function definition stored as a property value.
What are Object Methods?
When a function is stored inside an object, it is called an object method.
Accessing Object Methods:
You access an object method with the following syntax:
objectName.methodName()
If you invoke the fullName property with (), it will execute as a function:
Example
name = person.fullName();
If you access the fullName property without (), it will return the function definition:
Example
name = person.fullName;

eg 1
const Person = {
firstname:"Priya",
lastname:"saraswathi",
id: 5566,
fullname: function(){
return this.firstname + " " + this.lastname;
}
}
let fullname = Person.fullname();
console.log(fullname);
output
Priya saraswathi

eg 2
const Person = {
firstname:"Priya",
lastname:"saraswathi",
id: 5566,
fullname: function(){
return this.firstname + " " + this.lastname;
}
}
let fullname = Person.fullname();
console.log(Person.firstname);
output
Priya

Adding a Method to an Object
Adding a new method to an object is easy:
Example
person.name = function () {
return this.firstName + " " + this.lastName;
};

Using JavaScript Methods
This example uses the JavaScript toUpperCase() method to convert a text to uppercase:
Example
person.name = function () {
return (this.firstName + " " + this.lastName).toUpperCase();
};

Built-in Numbers
Number Properties (Static)

Number.MAX_VALUE

Definition:
Largest possible number in JavaScript.

console.log(Number.MAX_VALUE);
// 1.7976931348623157e+308

Number.MIN_VALUE

Definition:
Smallest positive number greater than 0.

console.log(Number.MIN_VALUE);
// 5e-324

Number.POSITIVE_INFINITY

Definition:
Represents positive infinity.

console.log(Number.POSITIVE_INFINITY);
// Infinity

Number.NEGATIVE_INFINITY

Definition:
Represents negative infinity.

console.log(Number.NEGATIVE_INFINITY);
// -Infinity

Number.NaN

Definition:
Represents “Not a Number”.

console.log(Number.NaN);
// NaN

Number.EPSILON

Definition:
Smallest difference between two representable numbers.

console.log(Number.EPSILON);
// 2.220446049250313e-16

Number.MAX_SAFE_INTEGER

Definition:
Largest safe integer in JavaScript.

console.log(Number.MAX_SAFE_INTEGER);
// 9007199254740991

Number.MIN_SAFE_INTEGER

Definition:
Smallest safe integer in JavaScript.

console.log(Number.MIN_SAFE_INTEGER);
// -9007199254740991

📌 Number Methods (Static)

Number.isNaN(value)

Definition:
Checks if value is NaN.

console.log(Number.isNaN(NaN)); // true
console.log(Number.isNaN("10")); // false

Number.isFinite(value)

Definition:
Checks if value is a finite number.

console.log(Number.isFinite(100)); // true
console.log(Number.isFinite(Infinity)); // false

Number.isInteger(value)

Definition:
Checks if value is an integer.

console.log(Number.isInteger(10)); // true
console.log(Number.isInteger(10.5)); // false

Number.isSafeInteger(value)

Definition:
Checks if value is a safe integer.

console.log(Number.isSafeInteger(100));
// true

Number.parseInt(value)

Definition:
Converts string to integer.

console.log(Number.parseInt("123.45"));
// 123

Number.parseFloat(value)

Definition:
Converts string to floating-point number.

console.log(Number.parseFloat("123.45"));
// 123.45

📌 Number Methods (Instance)

toString()

Definition:
Converts number to string.

let n = 10;
console.log(n.toString());
// "10"

toFixed(n)

Definition:
Formats number with n decimal places.

let x = 5.6789;
console.log(x.toFixed(2));
// "5.68"

toExponential(n)

Definition:
Converts number to exponential notation.

let x = 1234;
console.log(x.toExponential(2));
// "1.23e+3"

toPrecision(n)

Definition:
Formats number to n total digits.

let x = 123.456;
console.log(x.toPrecision(4));
// "123.5"

valueOf()

Definition:
Returns primitive value of number.

let x = new Number(10);
console.log(x.valueOf());
// 10

toLocaleString()

Definition:
Formats number based on locale.

let num = 1000000;
console.log(num.toLocaleString("en-IN"));
// "10,00,000"

Built-in BigInt

javascript

PRIYA K — Tue, 02 Dec 2025 12:09:29 +0000

Get ElementById() ,get ElemenyByTagname()
1

Take copy of Guhan

Take separate words from paragraph

<p id ="data"> GUhan </p>

document.getElementById("data").innerHTML

By value

Take text from browser which is already typed in browser

<input id ="data">  </input>

document.getElementById("data").value

move input to paragraph

Step 1: enter data
Chennai in (form)
<input id="from">

step 2: click the button
submit

step3: store value in box(memory)

step4:move data into innerHTML
<p id="to"> chennai </p>

<!DOCTYPE html>
<html lang="en">
<head>
    <title>Document</title>
    <script src=""></script>
    <style>
        input{width:40%;height:40px;}h2,p{color:red;}
        button{width:40%;height:40px;
        background-color: blue;color:white};
    </style>
</head>
<body>
    <h2> Select By Id</h2>
            <input id="from" placeholder="Enter Data"><br><br>
            <button>submit</button>
            <p id ="to"> </p>

</body>
</html>

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script src=""></script>
    <style>
        input{width:40%;height:40px;}h2,p{color:red;}
        button{width:40%;height:40px;
        background-color: blue;color:white};
    </style>
</head>
<body>
    <h2> Select By Id</h2>
            <input id="from" placeholder="Enter Data"><br><br>
            <button onclick="check()">submit</button>
            <p id ="to"> </p>
            <script>
                function check()
                {
                    box=document.getElementById("from").value;
                    document.getElementById("to").innerHTML = box;
                }
            </script>


</body>
</html>

4 move more input to paragraph

Dom Select by tag name

form

step1: enter first name
priya
step2:enter last name
saraswathi
step3: enter country
india
submit

stores values in memory as array

box
box[0]
box[1]
box[2]

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>

    <style>
        div {
            margin: auto;
            width: 600px;
            height: auto;
        }

        input {
            width: 100%;
            height: 40px;
            color: red;
            font-size: 18px;
        }

        h2 {
            color: green;
        }

        p {
            color: blue;
            font-size: 18px;
        }

        button {
            width: 100%;
            height: 40px;
            font-size: 18px;
            background-color: blue;
            color: white;
        }
    </style>
</head>

<body>
    <div>
        <h2>Select By Tag Name</h2>

        <input placeholder="Enter First Name"><br><br>
        <input placeholder="Enter Last Name"><br><br>
        <input placeholder="Enter Country Name"><br><br>

        <button onclick="check()">Submit</button>

        <p></p>
        <p></p>
        <p></p>
    </div>

    <script>
        function check() {
            let box = document.getElementsByTagName("input");
            let data = document.getElementsByTagName("p");

            data[0].innerHTML = box[0].value;
            data[1].innerHTML = box[1].value;
            data[2].innerHTML = box[2].value;
        }
    </script>

</body>

</html>

output

Select By Tag Name
enter first name: guhan
enter last name: ganesan
enter country name: india
submit

guhan
ganesan
india

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>

    <style>
        div {
            margin: auto;
            width: 600px;
            height: auto;
        }

        input {
            width: 100%;
            height: 40px;
            color: red;
            font-size: 18px;
        }

        h2 {
            color: green;
        }

        p {
            color: blue;
            font-size: 18px;
        }

        button {
            width: 100%;
            height: 40px;
            font-size: 18px;
            background-color: blue;
            color: white;
        }
    </style>
</head>

<body>
    <div>
        <h2>Select By Tag Name</h2>

        <input placeholder="Enter First Name"><br><br>
        <input placeholder="Enter Last Name"><br><br>
        <input placeholder="Enter Country Name"><br><br>

        <button onclick="check()">Submit</button>

        <p></p>
        <p></p>
        <p></p>
    </div>

    <script>
        function check()
                {
                    box=document.getElementByTagName("input");
                    data=document.getElementByTagName("p");

                    for(i=0;i<box.length;i++)
                {
                    data[i].innerHTML = box[i].value;
                    console.log(i);
                }
    </script>

</body>

</html>

select by tag name from id

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>

    <style>
        div {
            margin: auto;
            width: 600px;
            height: auto;
        }

        input {
            width: 100%;
            height: 40px;
            color: red;
            font-size: 18px;
        }

        h2 {
            color: green;
        }

        p {
            color: blue;
            font-size: 18px;
        }

        button {
            width: 100%;
            height: 40px;
            font-size: 18px;
            background-color: blue;
            color: white;
        }
    </style>
</head>

<body>

    <h2>Select By Tag Name</h2>

    <input placeholder="Enter Id"><br><br>

    <!-- Inputs inside this div so getElementsByTagName works -->
    <div id="mydiv">
        <input placeholder="Enter First Name"><br><br>
        <input placeholder="Enter Last Name"><br><br>
        <input placeholder="Enter Country Name"><br><br>
    </div>

    <button onclick="check()">Submit</button>

    <p></p>
    <p></p>
    <p></p>

    <script>
        function check() {
            let area = document.getElementById("mydiv");
            let box = area.getElementsByTagName("input");
            let data = document.getElementsByTagName("p");

            data[0].innerHTML = box[0].value;
            data[1].innerHTML = box[1].value;
            data[2].innerHTML = box[2].value;
        }
    </script>

</body>

</html>

output
enter id: 1234
enter first name:priya
enter last name:saraswathi
enter country:india

priya
saraswathi
india

6...

print hour


<body>

    <h2>Javascript Date</h2>

    <p id="p1"> </p>
    <button onclick="start()">start</button>
    <button onclick="stop()">stop</button>


    <script>
        date = new Date();
        hour = date.getHours();

        x=document.getElementById("p1");
        x.innerHTML = hour;
    </script>

</body>

</html>

print minute


<body>

    <h2>Javascript Date</h2>

    <p id="p1"> </p>
    <button onclick="start()">start</button>
    <button onclick="stop()">stop</button>


    <script>
        date = new Date();
        hour = date.getHours();
        minute = date.getMinutes();

        x=document.getElementById("p1");
        x.innerHTML = minute;
    </script>

</body>

</html>

print second


<body>

    <h2>Javascript Date</h2>

    <p id="p1"> </p>
    <button onclick="start()">start</button>
    <button onclick="stop()">stop</button>


    <script>
        date = new Date();
        hour = date.getHours();
        minute = date.getMiutes();
        second = date.getSeconds();
        timing = date.toLcaleTimeString();

        x=document.getElementById("p1");
        x.innerHTML = timing;


    </script>

</body>

</html>

date,set interval clear interval

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>

    <style>
        div {
            margin: auto;
            width: 600px;
            height: auto;
        }

        h2 {
            color: green;
        }

        p {
            color: blue;
            font-size: 30px;
            font-weight: bold;
        }

        button {
            width: 150px;
            height: 40px;
            font-size: 18px;
            background-color: blue;
            color: white;
            margin-right: 10px;
        }
    </style>
</head>

<body>

    <h2>Javascript Date</h2>

    <p id="p1"></p>
    <button onclick="start()">Start</button>
    <button onclick="stop()">Stop</button>

    <script>
        let clear; // for interval reference

        function changeColor() {
            let date = new Date();
            let timing = date.toLocaleTimeString();
            let second = date.getSeconds();

            let x = document.getElementById("p1");
            x.innerHTML = timing;

            if (second % 2 == 0) {
                x.style.color = "red";
            } else {
                x.style.color = "blue";
            }
        }

        function start() {
            clear = setInterval(changeColor, 1000);
        }

        function stop() {
            clearInterval(clear);
        }
    </script>

</body>

</html>

paste text into html element

create element

pass text "hi javascript"
in html body ,in div tag we are appending the "hi javascript" using element.appendchild(text)

ans
document.createElement("p")
document.createTextNode("Hi Javascript")

code

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>

    <style>
        div {
            margin: auto;
            width: 600px;
            height: auto;
        }

        h2 {
            color: green;
        }

        p {
            color: blue;
            font-size: 30px;
            font-weight: bold;
        }

        button {
            width: 150px;
            height: 40px;
            font-size: 18px;
            background-color: blue;
            color: white;
            margin-right: 10px;
        }
    </style>
</head>

<body>

    <h2>Create New HTML Element </h2>
    <div id = "mydiv">

    </div>
    <input placeholder="Enter data" id="myinput"><br><br>
    <button onclick="create()">submit</button>
    <script>
        function create()
        {
            value = document.getElementById("myinput").value;
            element = document.createElement("p");
            text = document.createTextNode(value);
            element.appendChild(text);
            mydiv=document.getElementById("mydiv");
            mydiv.appendChild(element);
        }
    </script>

</body>

</html>

chat app

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Chat App</title>

    <style>
        .container {
            margin: auto;
            width: 600px;
        }

        .box {
            padding: 10px;
            margin: 10px 0;
        }

        #mydiv {
            min-height: 200px;
            border: 2px solid black;
            margin-top: 10px;
        }

        li {
            font-size: 20px;
            list-style: none;
            margin: 5px 0;
        }
    </style>
</head>

<body>

    <h2>Chatting between two persons</h2>

    <div class="container">

        <div class="box" style="background-color: #FCF78F;">
            <h2>Person A</h2>
            <input id="i1">
            <button onclick="sendsms()">Send</button>
        </div>

        <ul id="mydiv" class="box"></ul>

        <div class="box" style="background-color: #FC8FF2;">
            <h2 style="color:red;">Person B</h2>
            <input id="i2">
            <button onclick="sendsms()">Send</button>
        </div>

    </div>

    <script>
        function sendsms() {
            let value1 = document.getElementById("i1").value;
            let value2 = document.getElementById("i2").value;

            let mydiv = document.getElementById("mydiv");
            let element = document.createElement("li");

            if (value1 !== "") {
                // Person A message
                let text1 = document.createTextNode(value1);
                element.appendChild(text1);
                element.style.color = "blue";
                mydiv.appendChild(element);
                document.getElementById("i1").value = "";
            }

            else if (value2 !== "") {
                // Person B message
                let text2 = document.createTextNode(value2);
                element.appendChild(text2);
                element.style.color = "red";
                mydiv.appendChild(element);
                document.getElementById("i2").value = "";
            }
        }
    </script>

</body>

</html>

Basic Calculator

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Basic Calculator</title>

    <style>
        table {
            border: 8px solid #010BDF;
            background-color: #566950;
        }

        input {
            width: 370px;
            height: 40px;
            background-color: #CAF6D6;
            color: red;
            font-size: 18px;
        }

        button {
            width: 70px;
            height: 50px;
            font-size: 18px;
        }

        h2 {
            color: #02087C;
        }

        body {
            background-color: #47FE97;
        }
    </style>
</head>

<body>

    <h2>JavaScript Standard Calculator</h2>

    <table>
        <tr>
            <td colspan="5"><input id="i1"></td>
        </tr>

        <tr>
            <td><button onclick="send(1)">1</button></td>
            <td><button onclick="send(2)">2</button></td>
            <td><button onclick="send(3)">3</button></td>
            <td><button onclick="send(4)">4</button></td>
            <td><button onclick="send(5)">5</button></td>
        </tr>

        <tr>
            <td><button onclick="send(6)">6</button></td>
            <td><button onclick="send(7)">7</button></td>
            <td><button onclick="send(8)">8</button></td>
            <td><button onclick="send(9)">9</button></td>
            <td><button onclick="send(0)">0</button></td>
        </tr>

        <tr>
            <td><button onclick="send('+')"> + </button></td>
            <td><button onclick="send('-')"> - </button></td>
            <td><button onclick="send('/')"> / </button></td>
            <td><button onclick="send('*')"> * </button></td>
            <td><button onclick="send('=')"> = </button></td>
        </tr>

        <tr>
            <td><button onclick="send('log')"> log </button></td>
            <td><button onclick="send('√')"> √ </button></td>
            <td><button onclick="send('1/x')"> 1/x </button></td>
            <td><button onclick="send('.')"> . </button></td>
            <td><button onclick="send('AC')"> AC </button></td>
        </tr>

    </table>

    <script>
        function send(i) {
            let x = document.getElementById("i1");

            switch (i) {

                case 0: x.value += "0"; break;
                case 1: x.value += "1"; break;
                case 2: x.value += "2"; break;
                case 3: x.value += "3"; break;
                case 4: x.value += "4"; break;
                case 5: x.value += "5"; break;
                case 6: x.value += "6"; break;
                case 7: x.value += "7"; break;
                case 8: x.value += "8"; break;
                case 9: x.value += "9"; break;

                case '+': x.value += "+"; break;
                case '-': x.value += "-"; break;
                case '*': x.value += "*"; break;
                case '/': x.value += "/"; break;
                case '.': x.value += "."; break;

                case 'AC':
                    x.value = "";
                    break;

                case 'log':
                    x.value = Math.log10(x.value);
                    break;

                case '√':
                    x.value = Math.sqrt(x.value);
                    break;

                case '1/x':
                    x.value = 1 / x.value;
                    break;

                case '=':
                    x.value = eval(x.value);
                    break;
            }
        }
    </script>

</body>

</html>

Refresh Auto-Refresh Page Redirection

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        h2{color:blue; font-size: 35px;}
        input{width: 40%;height: 40px;}
        button{width: 40%; height: 40px;
            background-color: blue;color:white;
            font-size: 22px;}
        body{background-color: #faf77B;}
    </style>
</head>
<body id="b1">
    <h2 id= "h2">refresh,Auto Refresh and Redirect the web page</h2>

    <input id="i1" placeholder="Assign Time To Refresh The Web Page"><br><br>
    <button onclick="Refresh()">click</button>

    <script>
        function Refresh()
        {
        time = document.getElementById("i1").value;
        time = parseInt(time);
        setTimeout("location.reload(true)",time*1000);
        console.log(window.location.href);
        if(setTimeout("location.reload(true)",time*1000))
        {
            document.getElementById("h2").style.color="red";
        }
        }
    </script>
</body>

</body>
</html>

14...

modify 13 by background colour

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        h2{color:blue; font-size: 35px;}
        input{width: 40%;height: 40px;}
        button{width: 40%; height: 40px;
            background-color: blue;color:white;
            font-size: 22px;}
        body{background-color: #faf77B;}
    </style>
</head>
<body id="b1">
    <h2 id= "h2">refresh,Auto Refresh and Redirect the web page</h2>

    <input id="i1" placeholder="Assign Time To Refresh The Web Page"><br><br>
    <button onclick="Refresh()">click</button>

    <script>
        function Refresh()
        {
        time = document.getElementById("i1").value;
        time = parseInt(time); //60*5*2
        setTimeout("location.reload(true)",time*1000);
        console.log(window.location.href);
        if(setTimeout("location.reload(true)",time*1000))
        {
            document.getElementById("b1").style.backgroundColor="red";
        }
        }
    </script>
</body>

</body>
</html>

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        h2{color:blue; font-size: 35px;}
        input{width: 40%;height: 40px;}
        button{width: 40%; height: 40px;
            background-color: blue;color:white;
            font-size: 22px;}
        body{background-color: #faf77B;}
    </style>
</head>
<body id="b1">
    <h2 id= "h2">refresh,Auto Refresh and Redirect the web page</h2>

    <input id="i1" placeholder="Assign Time To Refresh The Web Page"><br><br>
    <button onclick="Refresh()">click</button>

    <script>
        function Refresh()
        {
        // time = document.getElementById("i1").value;
        // time = parseInt(time); //60*5*2
        time = 3;
        setTimeout("location.reload(true)",time*1000);
        console.log(window.location.href);
        if(setTimeout("location.reload(true)",time*1000))
        {
            document.getElementById("b1").style.backgroundColor="red";
        }
        }
        setInterval(Refresh,3000);
    </script>
</body>

</body>
</html>

Redirection

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        h2{color:blue; font-size: 35px;}
        input{width: 40%;height: 40px;}
        button{width: 40%; height: 40px;
            background-color: blue;color:white;
            font-size: 22px;}
        body{background-color: #faf77B;}
    </style>
</head>
<body id="b1">
    <h2 id= "h2">refresh,Auto Refresh and Redirect the web page</h2>

    <input id="i1" placeholder="Assign Time To Refresh The Web Page"><br><br>
    <button onclick="Refresh()">click</button>

    <script>
        function Refresh()
        {
        // time = document.getElementById("i1").value;
        // time = parseInt(time); //60*5*2
        time = 3;
        setTimeout("location.reload(true)",time*1000);
        console.log(window.location.href);
        if(setTimeout("location.assign('https://payilagam.com/')",time*1000))
        {
            document.getElementById("b1").style.backgroundColor="red";
        }
        }
        setInterval(Refresh,3000);
    </script>
</body>

</body>
</html>

17....

Alert , Confirm ,Prompt Box

Alert Box

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        h2{color:blue; font-size: 35px;}
        p{width:40%;height:40px;color:red;font: size 25px;}
        button{width: 20%; height: 40px;
            background-color: blue;color:white;
            font-size: 22px;}
        body{background-color: #faf77B;}
    </style>
</head>
<body id="b1">
    <h2 id= "h2">Alert,Confirm,Prompt box...</h2>
    <p id="p1"></p>
    <button onclick="check()">click</button>

    <script>
        function check()
        {
        alert("Dont visit this page");
        }
    </script>
</body>

</body>
</html>

conform Box

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        h2{color:blue; font-size: 35px;}
        p{width:40%;height:40px;color:red;font: size 25px;}
        button{width: 20%; height: 40px;
            background-color: blue;color:white;
            font-size: 22px;}
        body{background-color: #faf77B;}
    </style>
</head>
<body id="b1">
    <h2 id= "h2">Alert,Confirm,Prompt box...</h2>
    <p id="p1"></p>
    <button onclick="check()">click</button>

    <script>
        function check()
        {
        if(confirm("sure to proceed"))
        {
            document.getElementById("p1").innerHTML="ThankYou";
        }
        else
        {
            document.getElementById("p1").innerHTML="Oh! sorry!";
        }
        }
    </script>
</body>

</body>
</html>

Prompt Box

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        h2{color:blue; font-size: 35px;}
        p{width:40%;height:40px;color:red;font: size 25px;}
        button{width: 20%; height: 40px;
            background-color: blue;color:white;
            font-size: 22px;}
        body{background-color: #faf77B;}
    </style>
</head>
<body id="b1">
    <h2 id= "h2">Alert,Confirm,Prompt box...</h2>
    <p id="p1"></p>
    <button onclick="check()">click</button>

    <script>
        function check()
        {
        password = prompt("enter a password")
        if(password ==1234)
        {
            document.getElementById("p1").innerHTML="ThankYou";
        }
        else
        {
            document.getElementById("p1").innerHTML="Oh! sorry!";
        }
    }
    </script>
</body>

</body>
</html>

ADD CLASS AND REMOVE CLASS

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        body{background-color: #8BFC6F;}
        input{background-color: #EAFAF1;color:blue;
            width:100%;height:35px;font-size:23px;}
        p{padding:6px;color:red;font-size: 22px;}
        h1{color:#030DE6;}
        table{border:0px solid blue;border-collapse: collapse;}

        td{
        border:0px solid blue;width:250;height:70;
        text-align: center;font-size: 30px;
        background-color: #cbb9b1;color:blue;
        text-align:left;padding: 10px;
        }
        .show{width:180px;font-size: 18px;
            height:30px;background-color: #001BDB;color:white;}
    </style>
</head>
<body>
    <h1> ADD CLASS AND REMOVE CLASS IN JAVASCRIPT</h1>
<table>
    <tr>
        <td> Name: </td>
        <td><input onmouseover="onMouseover(0)" onmouseout="onMouseout(0)"></input></td>
        <td> <p> </p> </td>
    </tr>

    <tr>
        <td> Father: </td>
        <td><input onmouseover="onMouseover(1)" onmouseout="onMouseout(1)"></input></td>
        <td> <p> </p> </td>
    </tr>

    <tr>
        <td> Mother: </td>
        <td><input onmouseover="onMouseover(2)" onmouseout="onMouseout(2)"></input></td>
        <td> <p> </p> </td>
    </tr>

    <tr>
        <td> Mobile:</td>
        <td><input onmouseover="onMouseover(3)" onmouseout="onMouseout(3)"></input></td>
        <td> <p> </p> </td>
    </tr>

</table>
<script>
    x = document.getElementsByTagName("input");
    y = document.getElementsByTagName("p");

    function onMouseover(i)
    {
        if(x[i].value=="")
    {
        y[i].innerHTML="Please fill this field";
        y[i].className="show";
    }

    }

    function onMouseout(i)
    {
        y[i].innerHTML="";
        y[i].classList.remove("show");
    }


</script>

Application form validation

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        body{background-color: #8BFC6F;}
        input{background-color: #EAFAF1;color:blue;
            width:100%;height:35px;font-size:23px;}
        p{padding:6px;color:red;font-size: 22px;}
        h1{color:#030DE6;}
        table{border:0px solid blue;border-collapse: collapse;}

        td{
        border:0px solid blue;width:250;height:70;
        text-align: center;font-size: 30px;
        background-color: #cbb9b1;color:blue;
        text-align:left;padding: 10px;
        }
        span{color:red;}
    </style>
</head>
<body>
    <h1> JAVASCRIPT FORM VALIDATION </h1>
<form action="image.html" onsubmit="return check()" autocomplete="off">
<table align="center">
    <tr>
        <td> Name:<span>**</span>  </td>
        <td><input id ="name"/> </td>
    </tr>

    <tr>
        <td> Father: </td>
        <td><input /> </td>
    </tr>

    <tr>
        <td> Mother:</td>
        <td><input /> </td>
    </tr>

    <tr>
        <td> Mobile:<span>**</span>  </td>
        <td><input id ="mobile"/> </td>
    </tr>

    <tr>
        <td colspan="2"><input type="submit" value="signup"/> </td>
    </tr>
</table>
</form>
<script>
    function check()
    {
        name = document.getElementById("name").value;
        mobile = document.getElementById("mobile").value;
        if(name=="")
    {
        alert("Please fill the name");
        return false;
    }
    else if(mobile=="")
    {
        alert("Please fill the mobile");
        return false;
    }
    }

</script>


</table>
</form>

HTML 5

PRIYA K — Mon, 24 Nov 2025 10:16:06 +0000

File -> Documents -> right click -> create new folder -> rename ->open -> create new document and click empty document ->rename as index.html

right click the index.html -> open with text editor -> type a message and save it

run the output: select the index.html file and double click

Structure of HTML

<!DOCTYPE HTML>(html follows the rule)
<html>
<head>(head contains container element.container element means keywords,page descriptions,author name,css file link)
<meta charset = "utf-8">(uses all languages)
<title>My Home Page</title>
</head>
<body>
   <h1>hi</h1>
   <p> this is </p>
</body>
</html>

metadata(data about data)
eg:

<meta name = "author" content = "priya">
<meta name = "description" content ="selenium">

1.Italic

<em>Priya</em>

output Priya

2.<!-- !>(for comment line)

3.Paragraph

<p>this is priya</p>

4.header tag

<h1>Priya</h1>
<h1> 5<10 </h1>
<h2>Priya</h2>
<h3>priya</h3>
<h4>priya</h4>
<h5>priya</h5>
<h6>priya</h6>

5.Attributes

<p class = "check">This is the table </p>

6.Link

<a href="www.kaniyam.com">Welcome To kaniyam</a>

<a href="www.kaniyam.com" title="Tamil Technology">Welcome To kaniyam</a>

7.open in another tab

<a href="www.kaniyam.com" title="Tamil Technology" target =_"blank">Welcome To kaniyam</a> (anchor tag)

8.boolean attributes(true ,false,on,off)

9.type in text box (get the input)

enter name:<input type="text">

10.disable the text box

enter name:<input type="text" disabled="disabled">

Character Entity Reference

greater than >
< lesser than <
" quotes "
' apostrophe '
& ampersand &

11.

to type in bigger size,use &lt;h1&gt; tag

output type in bigger size,use

tag

12.
unordered list:
ul-unordered list
li-list item

<ul>
   <li>Gandhi</li>
   <li>periyar</li>
   <li>netaji</li>
   <li>ambedhkar</li>
</ul>

output

Gandhi
periyar
netaji
ambedhkar

ordered list

<ol>
   <li>Gandhi</li>
   <li>periyar</li>
   <li>netaji</li>
   <li>ambedhkar</li>
</ol>

output

Gandhi
periyar
netaji
ambedhkar

nested list

<ol>
   <li>have pen and paper</li>
   <li>note down everything</li>
   <li>go through them</li>
   <li>ask questions
       <ul>
           <li>listen to the answer</li>
           <li>Raise again your questions on the answers</li>
       </ul>
   </li>
   <li>clarify your doubts</li>
</ol>

output

have pen and paper
note down everything
go through them
ask questions
listen to the answer
Raise again your questions on the answers
clarify your doubts
Emphasis

<p> It is good to <em> practise </em> regularly and <em> write </em> them. </p>

output
It is good to practise _regularly and _write them.

14.Underline

<p> HTML is <u>easy</u> to learn </p>

15.Combine strong,emphasis and underline

<p>HTML is <u><strong><em>easy </strong></em></u> to learn.

16.Description list
(ta(tamil) = default attribute)

<dl>
    <dt>HTML</dt>
    <dd>HTML is the standard markup language for Web pages.
        With HTML you can create your own Website.
        HTML is easy to learn - You will enjoy it!</dd>
    <dt>Kaniyam</dt>
    <dd><i lang = "ta">1960 முதல் 1990 வரை சோவியத் ரஷ்யாவில் இருந்து பல்வேறு பதிப்பகங்கள் தமிழ் உள்ளிட்ட பல மொழிகளில், அறிவியல், அரசியல், இலக்கியம், சிறார் இலக்கியம் எனப் பல்துறைகளில் பல நூல்களை வெளியிட்டன</i></dd>
</dl>

code

<dl>
    <dt><strong>HTML</strong></dt>
    <dd>HTML is the standard markup language for Web pages.
        With HTML you can create your own Website.
        HTML is easy to learn - You will enjoy it!</dd>
    <dt><strong><em>Kaniyam</em></strong></dt>
    <dd><i lang = "ta">1960 முதல் 1990 வரை சோவியத் ரஷ்யாவில் இருந்து பல்வேறு பதிப்பகங்கள் தமிழ் உள்ளிட்ட பல மொழிகளில், அறிவியல், அரசியல், இலக்கியம், சிறார் இலக்கியம் எனப் பல்துறைகளில் பல நூல்களை வெளியிட்டன</i></dd>
</dl>

17.abbrevations

<p>We use <abbr title ="Hyper Text Markup Language"> HTML </abbr> to structure our documents </p>

18.superscript and subscript

<p>HTML is the standard markup language <sup> for</sup> Web pages.With HTML you can create your own Website.

<p>HTML is the standard markup language <sub> for</sub> Web pages.With HTML you can create your own Website.

19.Marking up dates and times

<time datetime ="2025-11-23">20 June 2022</time>

20.Date Time

<time datetime ="2022-06-20">20 June 2022</time>

<time datetime ="2022-06"> June 2022</time>

<time datetime ="01-20"> 20 June </time>

<time datetime ="19:30"> 19:30 </time>

<time datetime ="19:30:01.856"> 9:30:01.856 </time>

<time datetime ="2022-01-20T19:30"> 7:30 pm, 20 June 2022 </time>

21.HyperLink

<p> Im creating a link to
<a href ="https://www.kaniyam.com/">Kaniyam Home Page </a>
</p>

Adding Attribute

<p> Im creating a link to
<a href ="https://www.kaniyam.com/" title = "The best place to learn">Kaniyam Home Page </a>
</p>

code

<a href="https://www.kaniyam.com/">
  <img src="linux.jpeg" alt ="Linux logo that links to the linux homepage">
</a>

Open link in new tab

<a href = "https://www.mozilla.org" target ="_blank"> Mozilla Foundation
</a>

Downloading attribute when linking to a download

<a href ="https://download.mozilla.org/?product = firefox - latest-ssl&os=linux64&lang=en-US"   download="firefox-latest-64bit-installer">
  Download latest Firefox for Linux(64-bit)(English , US)
</a>

Email Link:
mail to:Link indicates the email address of the intended recipient

<a href ="mailto:saraswathi@gmail.com"> Send mail to no one </a>
<a href ="mailto:saraswathi@gmail.com?-cc=yarum_illai@kaniyam.com&&bcc=nowhere@payilagam.com&subject =The%20subject%20of%20the%20email&body=The%20body%20of%20the%20email"> Send email with cc,bcc,subject and body
</a>

create Favicon

Highlighting

<p>Hi,I'm from <mark>Chennai </mark></p>

Image,Audio,Video

<img src="linux.jpeg" 
alt ="Tux The Penguin"

code

<img src="linux.jpeg" 
alt ="Tux The Penguin"
width ="400"
height ="324">

code

<img src="linux.jpeg" 
alt ="Tux The Penguin"
width ="400"
height ="324"
title ="Tux is a penguin character">

Figure (container)

<figure>
<img src="linux.jpeg" 
alt ="Tux The Penguin"
width ="400"
height ="324"
title ="Tux is a penguin character">
<figcaption>Linux-logo - Tux</figcaption>
</figure>

Video and Audio on the web:

<video src="rabbit.webm"controls>
  <p> Your browser doesn't support HTML5 video.Here is a <a href = "rabbit.webm">link to the video </a> instead. </p> </video>

code

<video controls>
 <source src="rabbit.mp4" type = "video.mp4">
 <source src="rabbit.webm" type = "video.webm">

  <p> Your browser doesn't support HTML5 video.Here is a <a href = "rabbit.mp4">link to the video </a> instead. </p> </video>

code

<video controls width = "400" height = "200"
   autoplay loop muted preload="auto"
   poster ="rabbit.jpeg"> <!-- try preload = "none" -->
   <source src="rabbit.mp4" type = "video.mp4">
   <source src="rabbit.webm" type = "video.webm">

code

<audio controls>
 <source src="viper.mp3" type ="audio/mp3">
 <source src="viper.ogg" type ="audio/ogg">
</audio>

Embedding Technologies:copy in youtube

= Embedding an entire web document inside another one


<pre class="highlight plaintext"><code>


code :copy in google maps




</code></pre>

<pre class="highlight plaintext"><code>

code



</code></pre>
<p>&lt;!DOCTYPE html&gt;<br>
<br>
  </p><br>
    <br>
    <title>Iframe with basic details</title><br>
  <br>
  <br>
    <h1>Iframe with basic details</h1><br>

width="100%" height="500" frameborder="0" allowfullscreen sandbox&gt;<br>
       <p> <a href="https://developer.mozilla.org/en-US/docs/glossary"> Fallback link for browsers that don't support iframes <br>
</a></p><br>
    <br>
   <br>

<pre class="highlight plaintext"><code>

Browsers Development Tools:



</code></pre>
<p>Shortcut: ctrl + shift + I or F12 or settings-&gt;web load pages<br>
<a href="https://en.wikipedia.org/wiki/Sandbox_(computer_security)">https://en.wikipedia.org/wiki/Sandbox_(computer_security)</a></p>
<pre class="highlight plaintext"><code>

Clickjacking
clickjacking is an interface-based attack that tricks website users into unwittingly clicking on malicious links.In clickjacking,the attackers embed their malicious links into buttons or legitimate pages in a website.In an infected site,whenever a user clicks on a legitimate link,the attacker gets the confidential information of that user ,which ultimately compromises the user's privacy on the Internet.

Courtesy:https://developer.mozilla.org/en-US/docs/Glossary/clickjacking

HTTPS:
https://letsencrypt.org/

Vector Graphics:

Images should not pixelate when we zoom them.
Two Types Of Images:
1.Raster Images
2.Vector Images

Raster Images:
Raster Images are defined using a grid of pixels.
Eg. .bmp, , .png, .jpg, .gif

Vector Images:
SVG[Scalable Vector Graphics] Format Images( .svg).
It is an XML-based language for describing vector images


code



</code></pre>
<p>&lt;!DOCTYPE html&gt;<br>
<br>
  </p><br>
    <br>
    <title> Vector versus raster </title><br>
  <br>
<br>
  <h1> Vector versus raster </h1><br>
  <img src="star.png" alt="A raster star"><br>
  <img src="star.svg" alt="A vector star"><br>
<br>


<p><svg width="300" height="200"><br>
   <rect width="100%" height="100%" fill="green"></rect><br>
</svg></p>
<pre class="highlight plaintext"><code>

Responsive Images:
CSS

span Tag:
div Tag:


code



</code></pre>
<table>
<td> first cell </td>
</table>
<pre class="highlight plaintext"><code>


code



</code></pre>
<table>
<td> first cell </td>
</table>
<pre class="highlight plaintext"><code>

(td = table data,th = table header)


code



</code></pre>
<table>
<th> first cell </th>
<td> first cell </td>
</table>
<pre class="highlight plaintext"><code>


code



</code></pre>
<table>
<th> first cell </th>
<td>
<strong> first cell </strong> </td>
</table>
<pre class="highlight plaintext"><code>


code



</code></pre>
<table>
<tr>
<td> first cell </td>
<td> second cell </td>
<td> third cell </td>
<td> fourth cell </td>
</tr>
</table>
<pre class="highlight plaintext"><code>


**code**



</code></pre>
<table>
<tr>
<th> first heading </th>
<th> second heading </th>
<th> third heading </th>
<th> fourth heading </th>
</tr>
<td> first cell </td>
<td> second cell </td>
<td> third cell </td>
<td> fourth cell </td>

</table>
<pre class="highlight plaintext"><code>


code



</code></pre>
<table>
  Monthly Electricity Bill 
 <tr>
    <th> Month </th>
    <th> Units </th>
</tr>
<tr>
    <td> January </td>
    <td> 100 </td>
</tr>
<tr>
    <td> February </td>
    <td> 50 </td>
</tr>
</table>
<pre class="highlight plaintext"><code>

code



</code></pre>
<table>
  <colgroup>
    <col span="2">
    <col>
   </colgroup>
   <tr>
      <th>Publisher</th>
      <th>Title</th>
      <th>Link</th>
   </tr>

   <tr>
       <td> Kaniyam </td>
       <td> CSS in tamil </td>
       <td> <a href="http://www.kaniyam.com/download/learn-css-in-tamil.pdf/">
       </a>
</td>
    </tr>

   <tr>
       <td> Kaniyam </td>
       <td> JavaScript in tamil </td>
       <td> <a href="http://www.kaniyam.com/download/learn-javascript-in-tamil.pdf/">
       </a>
</td>
    </tr>
</table>
<pre class="highlight plaintext"><code>


- &amp;nbsp--
- ensp - 2 spaces
- ensp - 4 space
- &lt;br&gt; = line break

**Nested Table**



</code></pre>
<table id="table1">
  <tr>
     <th> title1 </th>
     <th> title2 </th>
     <th> title3 </th>
  </tr>
  <tr>
     <td id="nested">
     <table id="table">
       <tr>
          <td> cell1 </td>
          <td> cell2 </td>
          <td> cell3 </td>
       </tr>
     </table>
     </td>
     <td> cell2 </td>
     <td> cell3 </td>
   </tr>
       <tr>
          <td> cell4 </td>
          <td> cell5 </td>
          <td> cell6 </td>
       </tr>
</table>
<pre class="highlight plaintext"><code>

Check Boxes:



</code></pre>
<h1> Check the Course you wish </h1>

<p> Java<br>
  </p>

<p><br>
 Python<br>
  </p>

<p><br>
 Angular<br>
  </p>

<p><br>
 React<br>
  </p>

<p></p>
<pre class="highlight plaintext"><code>


Radio Buttons:



</code></pre>
<p>HTML<br>
<h2>HTML</h2></p>

<p>CSS<br>
<h2>CSS</h2></p>

<p>JAVASCRIPT<br>
<h2>JAVASCRIPT</h2></p>
<pre class="highlight plaintext"><code>


Input Box - Password:



</code></pre>
<p><br>
<br>
 <h3> Password:</h3> <br><br>
<br>
<br><br><br>
 <h2> Choose Course </h2> </p>
<pre class="highlight plaintext"><code>

Drop Down / Select Box



</code></pre>
<p><br>
   Java <br>
   Python <br>
   Ruby<br>
   .NET <br>
</p>
<pre class="highlight plaintext"><code>

code



</code></pre>
<p><br>
   Select Course <br>
   Java <br>
   Python <br>
   Ruby<br>
   .NET <br>
</p>
<pre class="highlight plaintext"><code>

</code></pre>

GIT COMMANDS

PRIYA K — Sat, 22 Nov 2025 22:57:02 +0000

*INSTALLATION *
step 1:Register -> sign in ->sign up in GITLAB
step 2: Install VisualStudio
step 3:

In Command Prompt
Copy - ctrl + shift + C
Paste - ctrl + shift + V

Command Prompt

1. check the Git Version
   git --version
2. Install Git by command
   sudo apt install git
   password: Welcome@123
   y / n
   y
3. Updating latest Version
   sudo apt update
4. Updating System
   sudo apt upgrade

step 4:
In GITLAB
Group -> New group -> Create Group -> Group Name -> Visibility level -> Public -> Who will be using this group? Just me -> Create Group

step 5: Click Project -> Create Blank Project -> give project name -> Change Visibility Level -> Create Project

GIT CLONE
Step 1: In GITLAB
Select Group -> Project -> Click that particular Project -> Code -> Clone with HTTPS -> Copy URL

Step 2: Select Location in Computer Folder
File Manager -> Documents -> right click -> create New Folder -> Select that particular folder ,right click -> Open In Terminal

step 3:
In Command Prompt:

git clone (Paste the copied URL)

Working Directory to Remote Repository
step 1: select the particular folder location in computer
open in terminal(creating txt file in computer folder)

git status
touch file1.txt
git status

step 2: change untracked file into tracked file(working file to staging area)
open in terminal

git add file1.txt
git status

If you want to untracked the file

git restore --staged file1.txt
git status

Add all files

git add .
git status

step 3: change staging area files to local repository

git commit -m "learn git"
git config --global user.name"priya K"
git config --global user.email priya.k.2021.ad@ritchennai.edu.in
git config --list

step 4: local repository file to remote repository

git status
git log (see commit message)
git push 
username:
password:

check the file in remote repository

Edit the file in Remote Repository (write in gitlab file) and working directory
step 1: Edit the file in Remote Repository
gitlab-> project ->click file1.txt file(empty file) -> edit -> open in web IDE(type a mesage in txt file) -> save the file as ctrl + s
-> branch symbol in left corner(click that symbol)->give commit message -> commit to main -> continue
step 2:Edit the file in working directory
select the folder in computer location
give right click -> open in terminal
open in terminal

git status(nothing to commit)
git pull

open the file in working directory

delete the file
in computer folder -> select the file and delete it.
open in terminal

git clear
git status
git add file1.txt
git status
git clear
git commit -m "deleted"
git push
username
password

deleted that file in gitlab

create a file in computer folder

touch file2.txt(create a file in computer folder)
git status
git add .
git commit -m "second"
git push
username:
password:

rename a file
in computer folder -> right click -> rename ->git status

git add file1.txt
git commit -m"one file"
git push
username:
password:

git add .
git commit -m"second file"
git push
username :
password :

deleted file2.txt

git log
q(to come out)

git log --oneline

git diff
select the folder in computer location -> open with notepad ->type a message and save it (ctrl + S)

in terminal

git diff

git status(nothing to commit)
git branch

**create a branch**

syntax : git branch branch_name

git branch test
git branch
ls(list of file)(linux command)

go from one branch to another branch
syntax: git checkout branchname

git checkout test(switched to test)
git branch
ls

Rename the branch name
syntax : git branch -m oldname newname

git branch -m test testing
git branch

delete the branch
syntax: git branch --delete branchname

git branch --delete testing
git branch
git checkout main
git branch
git branch --delete test
git branch

deleted branch test

git conflict
after pushing the file
in gitlab -> edit -> open in webid -> type a message and save it(ctrl + s) -> branch symbol at left corner -> commit to main

refresh the file in gitlab

type another message in webid
click that file in computer location and right click and open in terminal

git status(modified)
git pull
username:
password:
(overwritten error)
git stash
git pull
username:
password:

open in both open in webid and gitlab

take back from stash

git stash pop

change the message in webid and save it(ctrl + s)
open in terminal

git status(modified)
git add .
git commit -m"learn commit"
git push
username:
password:

conform by opening in gitlab

git merge

git branch
git branch develop(create a branch)
git branch
git checkout develop(move to develop branch)
git branch

type a message in webid and save it
open in terminal

git status(modified)
git add file1
git status
git commit -m"commited from dev branch"
git checkout main
git status
git branch

reflect the changes from develop branch to main branch
open in terminal

git merge develop
git push
username:
password:

open that file in gitlab main branch

GIT

PRIYA K — Sat, 22 Nov 2025 16:31:50 +0000

GIT(Global Information System).
Version Control System.
A tool that helps developers track changes in their code over time and allows multiple people to work on the same project at once,even offline.
Created by Linus Torvalds in 2005 for developing the Linux Kernel.
It lets you record snapshots of your project (called commits) so you can:
Go back to earlier version if needed.
See who made what changes .
Work on the same project with others without overwriting each others work.
GIT is used to collaborate on code.
GIT helps you keep track of code changes.

GITHUB
GITHUB is a web-based GIT repository hosting service.

GITHUB alternatives
Bit Bucket
Git Bucket

INSTALLATION
step 1:Register -> sign in ->sign up in GITLAB
step 2: Install VisualStudio
step 3:

In Command Prompt
Copy - ctrl + shift + C
Paste - ctrl + shift + V

Command Prompt

1. check the Git Version
   git --version
2. Install Git by command
   sudo apt install git
   password: Welcome@123
   y / n
   y
3. Updating latest Version
   sudo apt update
4. Updating System
   sudo apt upgrade

step 4:
In GITLAB
Group -> New group -> Create Group -> Group Name -> Visibility level -> Public -> Who will be using this group? Just me -> Create Group

step 5: Click Project -> Create Blank Project -> give project name -> Change Visibility Level -> Create Project

GIT CLONE
Step 1: In GITLAB
Select Group -> Project -> Click that particular Project -> Code -> Clone with HTTPS -> Copy URL

Step 2: Select Location in Computer Folder
File Manager -> Documents -> right click -> create New Folder -> Select that particular folder ,right click -> Open In Terminal

step 3:
In Command Prompt:

git clone (Paste the copied URL)

If you want to change the visibility level:
change public to private by,
step 1:Click the profile on top right corner
step 2: Click Group -> Click Group Name -> Settings -> general -> Change public into private -> Saved changes

Need to Know in Simple words
ReadMe : products catlogue
Config : connect GIT and GITLAB
Clone : Copy
SSH : secured shocket
It is used by password and gateways.

Questions

1... Git and Gitlab

git :

Distributed version control system
multiple developers works on same code base
merge
local machine gitlab:

web based devops platform
software development life cycle

analysis
plan
design
develop
test
deploy
1. CI/CD

2...Difference between distributed version control system vs centralised version control system

3...Git Conflict

Stash
Stash Pop