Forem: Kesavarthini

Looping Programs

Kesavarthini — Mon, 06 Apr 2026 14:21:18 +0000

1) Prime Number
i)Finding whether the given number is prime or not:

let num = 7;
let isPrime = true;

for (let i = 2; i < num; i++) {
    if (num % i === 0) {
        isPrime = false;
        break;
    }
}

if (num > 1 && isPrime) {
    console.log("Prime");
} else {
    console.log("Not Prime");
}

Output:

Prime

ii)Printing all the prime numbers within the 2-50:

for (let num = 2; num <= 50; num++) {

    let isPrime = true;

    for (let i = 2; i < num; i++) {
        if (num % i === 0) {
            isPrime = false;
            break;
        }
    }

    if (isPrime) {
        console.log(num);
    }
}

Output:

2) Reverse Printing a Number

        let num=1234;
        let reverse=0;
        while(num>0){
            let digit=num%10;
            reverse=reverse*10+digit;
            num=Math.floor(num/10);
        }
        document.write("Reverse: "+reverse);

Output:

Reverse: 4321

3) Count of Digits

        let num=1234;
        let count=0;
        while(num>0){
            let digit=num%10;
            num=Math.floor(num/10);
            count++;
        }
        document.write("Count of digits: "+count);

Output:

Count of digits: 4

4) Sum of Digits

let num = 123;
let sum = 0;

while (num > 0) {
    let digit = num % 10;
    sum += digit;
    num = Math.floor(num / 10);
}

console.log("Sum:", sum);

Output:

5) Palindrome

let num = 121;
let temp = num;
let reverse = 0;

while (num > 0) {
    let digit = num % 10;
    reverse = reverse * 10 + digit;
    num = Math.floor(num / 10);
}

if (temp === reverse) {
    console.log("Palindrome");
} else {
    console.log("Not Palindrome");
}

Output:

Palindrome

6) Swapping two numbers

let a = 5;
let b = 10;

let temp = a;  // store a
a = b;         // assign b to a
b = temp;      // assign temp to b

console.log("a =", a);
console.log("b =", b);

Output:

a = 10
b = 5

7) Swapping without third variable

let a = 5;
let b = 10;

a = a + b; // 15
b = a - b; // 5
a = a - b; // 10

console.log("a =", a);
console.log("b =", b);

Output:

a = 10
b = 5

Looping Statements in JS

Kesavarthini — Mon, 06 Apr 2026 12:53:17 +0000

Looping Statements in JavaScript

Looping statements in JavaScript are used to repeat a block of code multiple times until a condition becomes false.
Instead of writing the same code again and again, loops help make the code shorter and easier to manage.

JavaScript mainly provides the following loops:

1) for Loop

The for loop is used when we know how many times the loop should run.

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

Output:

Here, the loop starts from 1 and runs until 5.

2) while Loop

The while loop runs as long as the given condition is true.

let i = 1;
while (i <= 5) {
    console.log(i);
    i++;
}

This also prints numbers from 1 to 5.

3) DO...WHILE LOOP

Similar to while, but runs at least once (even if condition is false)

let i = 6;
do {
    console.log(i);
    i++;
} while (i <= 5);

Output:

Code must run at least once in do-while loop

Example Programs:
Looping Programs in JavaScript

1) 1 1 1 1 1
Print the number 1 five times.

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

Output:

2) 1 2 3 4 5
Print numbers from 1 to 5.

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

Output:

3) 1 3 5 7 9
Print the first five odd numbers.

for (let i = 1; i <= 9; i += 2) {
    console.log(i);
}

Output:

4) 3 6 9 12 15
Print multiples of 3.

for (let i = 1; i <= 5; i ++) {
    console.log(i*3);
}

Output:

5) Multiples of 3 and 5

<!DOCTYPE html>
<html>
    <head>
    <title>document</title>
    </head>
    <body>
        <script>

        for(let i=1;i<=30;i++){
            if(i%3===0 && i%5===0){
                document.write("Multiples of 3 and 5:"+i+ "<br>");
            }
        }
</script>
    </body>
</html>

Output:

Multiples of 3 and 5:15
Multiples of 3 and 5:30

6) Multiples of 3 or 5

<!DOCTYPE html>
<html>
    <head>
    <title>document</title>
    </head>
    <body>
        <script>

        for(let i=1;i<=30;i++){
            if(i%3===0 || i%5===0){
                document.write(i+"<br>");
            }
        }
</script>
    </body>
</html>

Output:

7) Divisors of given number

<!DOCTYPE html>
<html>
    <head>
    <title>document</title>
    </head>
    <body>
        <script>

        let num=10;
        for(let i=1;i<=num;i++){
            if(num%i==0){
                document.write(i+" ");
            }
        }
</script>
    </body>
</html>

Output:

1 2 5 10

8) Count of Divisors of given number

<!DOCTYPE html>
<html>
    <head>
    <title>document</title>
    </head>
    <body>
        <script>

        let num=10;
        let count=0;
        for(let i=1;i<=num;i++){
            if(num%i==0){
                document.write(Divisors of 10:+" ");
                count++
            }

        }
        document.write("<br>");
        document.write("Count:"+count);
</script>
    </body>
</html>

Output:

Divisors of 10:1 2 5 10 
Count:4

Scenario Based Questions-Conditional Statements in JS

Kesavarthini — Wed, 01 Apr 2026 13:04:48 +0000

1) Shopping Discount System

let amount = 6000;
let isMember = true;
let discount = 0;

if (amount >= 5000) {
    discount = 0.20;
} else if (amount >= 2000) {
    discount = 0.10;
}

if (isMember) {
    discount += 0.10;
}

let finalPrice = amount - (amount * discount);

console.log("Final Price:", finalPrice);

2) Login Access Check

let username = "admin";
    let password = "1234";
    let isBlocked = false;

    if (username == "admin") {
        if (password == "1234") {
            if (!isBlocked) {
                console.log("User verified");
            }
            else {
                console.log("User blocked");
            }
        }
        else {
            console.log("Incorrect password");
        }
    }
    else {
        console.log("Incorrect username");
    }

3) Traffic Signal System

let signal = "red";

switch (signal) {
    case "red":
        console.log("Stop");
        break;
    case "yellow":
        console.log("Get Ready");
        break;
    case "green":
        console.log("Go");
        break;
    default:
        console.log("Invalid signal");
}

4) ATM Withdrawal

let balance = 5000;
let withdrawAmount = 2000;

if (withdrawAmount > balance) {
    console.log("Insufficient funds");
} else if (withdrawAmount <= 0) {
    console.log("Invalid amount");
} else {
    balance -= withdrawAmount;
    console.log("Remaining Balance:", balance);
}

5) Mobile Data Usage

let usage = 90;

    if (usage >= 100) {
        console.log("Limit exceeded");
    }
    else if (usage >= 80) {
        console.log("Warning: nearing limit");
    }
    else {
        console.log("Usage normal");
    }

Decision Making in JavaScript

Kesavarthini — Tue, 31 Mar 2026 12:43:17 +0000

🔀 Decision Making in JavaScript
Programs need to take decisions based on conditions, and JavaScript provides multiple ways to do that.

📌 1. if, else, else if

These are used to execute code based on conditions.

🔹 if Statement

if statement executes a block of code when a condition is true

let age = 18;

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

Nested if
You can use an if statement inside another if statement:

let age = 16;
let country = "USA";

if (country == "USA") {
  if (age >= 16) {
    console.log("You can drive!");
  }
}

🔹 if-else Statement
Use the else statement to specify a block of code to be executed if a condition is false.

let age = 16;

if (age >= 18) {
    console.log("Eligible");
} else {
    console.log("Not Eligible");
}

🔹 The else if Statement
Use the else if statement to specify a new condition if the first is false.

let marks = 75;

if (marks >= 90) {
    console.log("Grade A");
} else if (marks >= 60) {
    console.log("Grade B");
} else {
    console.log("Grade C");
}

📌 2. switch Statement

Used when we have multiple conditions based on a single value.
switch is often used as a more readable alternative to many if...else if...else statements, especially when dealing with multiple possible values.

let day = 2;

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

This is how it works:

The switch expression is evaluated once.
The value of the expression is compared with the values of each case.
If there is a match, the associated block of code is executed.
If there is no match, no code is executed.

The break Keyword

When JavaScript reaches a break keyword, it breaks out of the switch block.
This will stop the execution inside the switch block.
No more statements in the switch block will be executed.
The break keyword is crucial for preventing a "fall-through."
Without break, the code will continue to execute the next case blocks (and the default block if present) even if their values do not match the expression.

📌 3. Truthy and Falsy Values
In JavaScript, values are treated as true or false in conditions.

🔹 Truthy Values
👉 Everything else is truthy.

Examples:

Non-zero numbers: 42, -1, 3.14
Non-empty strings: "hello", "0", " "
Objects and arrays: {}, []
Functions: function() {}
Dates: new Date()
Symbols: Symbol()
BigInt values other than 0n: 10n

🔹 Falsy Values

false
0 (and -0)
0n (BigInt zero)
"" (empty string)
null
undefined
NaN

🔹 Example

let name = "";

if (name) {
    console.log("Name is present");
} else {
    console.log("Name is empty");
}

Output:

Name is empty

Operators in JavaScript

Kesavarthini — Tue, 31 Mar 2026 12:05:35 +0000

📌 What are Operators?

Operators are symbols used to perform operations on variables and values.

👉 Example:

let result = 10 + 5;

Here, + is an operator.

🧠 Types of Operators in JavaScript

JavaScript provides different types of operators:

🔹 1. Arithmetic Operators

Used for mathematical calculations.

Operator	Description
+	Addition
-	Subtraction
*	Multiplication
/	Division
%	Modulus (remainder)
++	Increment
--	Decrement

Example:

let a = 10;
let b = 3;

console.log(a + b); // 13
console.log(a % b); // 1

🔹 2. Assignment Operators

Used to assign values to variables.

Operator	Example
=	x = 10
+=	x += 5
-=	x -= 2
*=	x *= 3
/=	x /= 2

Example:

let x = 10;
x += 5; // x = 15

🔹 3. Comparison Operators

Used to compare values.

Operator	Description
==	Equal (value only)
===	Strict equal (value + type)
!=	Not equal
>	Greater than
<	Less than

Example:

console.log(5 == "5");   // true
console.log(5 === "5");  // false

🔹 4. Logical Operators

Used to combine conditions.

1. AND (&&)

👉 Returns true only if both conditions are true

✅ Example:

let a = 10;
let b = 5;

console.log(a > 5 && b > 2);  // true
console.log(a > 5 && b > 10); // false

2. OR (||)

👉 Returns true if at least one condition is true

✅ Example:

let a = 10;
let b = 5;

console.log(a > 5 || b > 10); // true
console.log(a < 5 || b > 10); // false

3. NOT (!)

👉 Reverses the result

✅ Example:

let isStudent = true;

console.log(!isStudent); // false

🔹 5. Unary Operators

Works with a single value.

let x = 5;

console.log(++x); // 6
console.log(--x); // 5

🔹 6. Ternary Operator

Shortcut for if-else condition.

let age = 18;

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

📌 What is a Type Operator?

A type operator is used to find the data type of a variable.

🔹 typeof Operator

typeof is used to check the type of a value.

✅ Examples:

console.log(typeof 10);        // number
console.log(typeof "Hello");   // string
console.log(typeof true);      // boolean
console.log(typeof undefined); // undefined
console.log(typeof null);      // object (special case)

📌 What is Type Coercion?

Type coercion means:

👉 Automatic conversion of one data type to another by JavaScript

🔄 Types of Coercion
🔹 1. Implicit Coercion (Automatic)

JavaScript converts types automatically.

Example:

console.log("5" + 2);  // "52"
console.log("5" - 2);  // 3
console.log("5" * 2);  // 10

👉 + converts to string
👉 -, * convert to number

🔹 2. Explicit Coercion (Manual)

We manually convert types.

Example:

Number("10");   // 10
String(100);    // "100"
Boolean(1);     // true

🔥 Common Examples

console.log(true + 1);   // 2
console.log(false + 1);  // 1
console.log(null + 1);   // 1

⚠️ Important Rules
"5" + 2 → String
"5" - 2 → Number
true → 1
false → 0

JavaScript Basics

Kesavarthini — Mon, 30 Mar 2026 14:15:34 +0000

🌐 What is JavaScript and How It Works?
JavaScript is a high-level scripting language used to add functionality to web pages.

👉 It controls how a website behaves.

🔹 Example:

Button click actions
Form validations
Showing alerts
Animations
Dynamic content updates

🧠 Where JavaScript is Used?

🌐 Websites (Frontend)
⚙️ Server-side apps (Node.js)
📱 Mobile apps (React Native)
🎮 Games and interactive apps

⚙️ How JavaScript Works?

JavaScript runs inside a web browser.

🔹 Step-by-step working:

You write JavaScript code

Example:

console.log("Hello World");

2. Browser receives the code

When you open a webpage, the browser loads HTML, CSS, and JavaScript.

3. JavaScript engine executes it

Every browser has a JavaScript Engine:

Chrome → V8 engine
Firefox → SpiderMonkey
Safari → JavaScriptCore

4. Code is executed line by line

JavaScript is interpreted, so it runs step by step.

5. Output is shown

Example output:
Hello World

Simple Real-Life Example

👉 Think of a website like a car:

HTML → Structure (body of car)
CSS → Design (paint & look)
JavaScript → Engine (makes it move)

⚡ Important Features of JavaScript

Runs in browser
Easy to learn
Lightweight language
Supports dynamic behavior
Works with HTML & CSS

🎯 Example Program

let name = "Akalya";

console.log("Welcome " + name);

Output:

Welcome Akalya

🧠 Data Types in JavaScript

JavaScript has two main types of data:

🔹 1. Primitive Data Types

Number → 10, 20
String → "Hello"
Boolean → true, false
Undefined → variable declared but not assigned
Null → empty value

Example:

let age = 20;
let name = "JS";
let isStudent = true;

🔹 2. Non-Primitive Data Types

Array → list of values
Object → collection of key-value pairs

Example:

let numbers = [1, 2, 3];

let person = {
  name: "John",
  age: 25
};

✍️ Variables in JavaScript

Variables are used to store data.

We can declare variables using:

🔹 var

var x = 10;

🔹 let

let y = 20;

🔹 const

const z = 30;

Difference Between var, let, const
var

Old method
Can redeclare
Can change value

let

Modern
Cannot redeclare
Can change value

const

Constant
Cannot redeclare
Cannot change value

🎯 Simple Example

let name = "JavaScript";
const version = 2024;

console.log(name);
console.log(version);

Method Overloading Tasks

Kesavarthini — Fri, 20 Mar 2026 13:22:40 +0000

Method Overloading Tricky Questions :

class Test {
    void show(int a) { }
    void show(long a) { }

    public static void main(String[] args) {
        Test t = new Test();
        t.show(10);
    }
}

ANSWER: show(int a)
10 is int → exact match is preferred over widening (int → long)

class Test {
    void show(Integer a) { }
    void show(int a) { }

    public static void main(String[] args) {
        Test t = new Test();
        t.show(10);
    }
}

ANSWER: show(int a)
Exact primitive match is preferred over autoboxing (int → Integer)

class Test {
    void show(int a, float b) { }
    void show(float a, int b) { }

    public static void main(String[] args) {
        Test t = new Test();
        t.show(10, 10);
    }
}

ANSWER: Compile-time error (Ambiguous)
Both require one widening conversion → compiler confused

class Test {
    void show(int... a) { }
    void show(int a) { }

    public static void main(String[] args) {
        Test t = new Test();
        t.show(10);
    }
}

ANSWER: show(int a)
Normal method > varargs

class Test {
    void show(int a) { }
    void show(int... a) { }

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

ANSWER: show(int... a)
Only varargs can take zero arguments

class Test {
    void show(double a) { }
    void show(float a) { }

    public static void main(String[] args) {
        Test t = new Test();
        t.show(10);
    }
}

ANSWER: show(double a)
10 is int → prefers wider type with better precision match → double

class Test {
    void show(Object o) { }
    void show(String s) { }

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

ANSWER: show(String s)
More specific type is chosen (String < Object)

class Test {
    void show(String s) { }
    void show(Integer i) { }

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

ANSWER: Compile-time error (Ambiguous)
Both are unrelated → compiler can’t decide

class Test {
    void show(int a, int b) { }
    void show(int... a) { }

    public static void main(String[] args) {
        Test t = new Test();
        t.show(10,20);
    }
}

ANSWER: show(int a, int b)
Fixed argument method > varargs

class Test {
    void show(int a) { }
    static void show(int a) { }

    public static void main(String[] args) {
        Test t = new Test();
        t.show(10);
    }
}

ANSWER: Compile time error
Static/non-static doesn’t matter → same signature

class Test {
    void show(long a) { }
    void show(float a) { }

    public static void main(String[] args) {
        new Test().show(10);
    }
}

ANSWER: Compile time error(Ambiguous)
int → long and int → float both valid → confusion

class Test {
    void show(int a) { }
    void show(int a, int... b) { }

    public static void main(String[] args) {
        new Test().show(10);
    }
}

ANSWER: show(int a)
Exact match beats varargs

class Test {
    void show(char c) { }
    void show(int i) { }

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

ANSWER: show(char c)
Exact match (char) preferred over widening (char → int)

class Test {
    void show(byte b) { }
    void show(short s) { }

    public static void main(String[] args) {
        byte b = 10;
        new Test().show(b);
    }
}

ANSWER: show(byte b)

class Test {
    void show(Object o) { }
    void show(String s) { }
    void show(CharSequence c) { }

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

ANSWER: show(String s)

Exception Handling Tasks

Kesavarthini — Mon, 16 Mar 2026 08:13:50 +0000

Here we check whether each block is valid or syntax error according to Exception Handling rules.

Java Rules

try must be followed by at least one catch or finally.
catch blocks must come after try.
finally must be last.
Child exception must come before parent exception


try {
} finally {
}

✅ Valid – try can have only finally.

try {
} catch(Exception e) {
}

✅ Valid

try {
} catch(Exception e) {
} finally {
}

✅ Valid

try {
} catch(ArithmeticException e) {
} catch(Exception e) {
}

✅ Valid
Child exception first, then parent.

try {
} catch(Exception e) {
} catch(ArithmeticException e) {
}

❌ Syntax Error
Parent exception (Exception) comes before child (ArithmeticException).
Child catch becomes unreachable.

try {
} finally {
} catch(Exception e) {
}

❌ Syntax Error
catch cannot come after finally.

try {
} catch(ArithmeticException e) {
} finally {
} catch(Exception e) {
}

❌ Syntax Error
catch cannot appear after finally.

try {
} catch(Exception e) {
} finally {
} finally {
}

❌ Syntax Error
Only one finally block is allowed.

try {
}

❌ Syntax Error
try must have catch or finally.

catch(Exception e) {
}

❌ Syntax Error
catch cannot exist without try.

finally {
}

❌ Syntax Error
finally cannot exist without try.

try {
} catch(ArithmeticException e) {
} catch(ArithmeticException e) {
}

❌ Syntax Error
Duplicate catch block for the same exception.

try {
} catch(Exception e) {
} catch(RuntimeException e) {
}

❌ Syntax Error
RuntimeException is a child of Exception, so this catch is unreachable.

try {
} catch(RuntimeException e) {
} catch(Exception e) {
}

✅ Valid
Child exception first, then parent.

try {
} finally {
} finally {
}

❌ Syntax Error
Only one finally block allowed.

Exception Handling Tasks

Kesavarthini — Mon, 16 Mar 2026 08:04:28 +0000

1. Division Program :

public class DivisionTest {
    public static void main(String[] args) {
        int a = 10;
        int b = 0;

        int result = a / b;
        System.out.println("Result: " + result);
    }
}

Handled Exception Source code:

public class DivisionTest {
    public static void main(String[] args) {
        int a = 10;
        int b = 0;

        try {
            int result = a / b;
            System.out.println("Result: " + result);
        } 
        catch (ArithmeticException e) {
            System.out.println("Cannot divide by zero");
        }

    }
}

2. Array Index Program :

public class ArrayTest {
    public static void main(String[] args) {
        int arr[] = {10, 20, 30, 40};

        System.out.println(arr[5]);
    }
}

Handled Exception Source code:

public class ArrayTest {
    public static void main(String[] args) {
        try {
            int arr[] = {10, 20, 30, 40};
            System.out.println(arr[5]);
        } catch (ArrayIndexOutOfBoundsException e) {
            //System.out.println("Index 5 out of bounds for length 4");
            System.out.println(e.getMessage());

        }
    }
}

3. String Conversion Program :

public class NumberFormatTest {
    public static void main(String[] args) {
        String s = "ABC";

        int num = Integer.parseInt(s);
        System.out.println(num);
    }
}