🔹 1. Variables

Variables are used to store data.

✅ var

• Old way to declare variables
• Function-scoped (not block-scoped)

var name = "Aditya";

✅ let

• Modern way (recommended)
• Block-scoped
• Value can be changed

let age = 25;
age = 30;

✅ const

• Block-scoped
• Value cannot be reassigned

const pi = 3.14;

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🔹 2. Data Types

📌 String

Text values

let name = "Aditya";

📌 Number

Numbers (integer or decimal)

let marks = 95;
let price = 99.99;

📌 Boolean

True or False

let isLogin = true;

📌 Undefined

Variable declared but not assigned

let x;

📌 Null

Empty value (intentionally)

let data = null;

📌 Object

Collection of key-value pairs

let user = {
  name: "Aditya",
  age: 25
};

📌 Array

List of values

let fruits = ["Apple", "Banana", "Mango"];

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🔹 3. Operators

➕ Arithmetic Operators

Used for calculations

let a = 10;
let b = 5;console.log(a + b); // 15
console.log(a - b); // 5
console.log(a * b); // 50
console.log(a / b); // 2

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🔍 Comparison Operators

Compare values (returns true/false)

console.log(10 == "10");   // true (loose)
console.log(10 === "10");  // false (strict)
console.log(10 > 5);       // true

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🔗 Logical Operators

Used with conditions

let age = 20;console.log(age > 18 && age < 30); // true
console.log(age > 18 || age < 10); // true
console.log(!(age > 18));          // false

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📝 Assignment Operators

Assign values

let x = 10;
x += 5;  // x = x + 5 → 15
x -= 2;  // 13

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🔹 4. Type Conversion

📌 Convert to String

let num = 100;
String(num); // "100"

📌 Convert to Number

let str = "50";
Number(str); // 50

📌 Convert to Boolean

Boolean(1); // true
Boolean(0); // false

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🧪 Practice Programs

✅ 1. Calculator Program

let a = 10;
let b = 5;console.log("Add:", a + b);
console.log("Subtract:", a - b);
console.log("Multiply:", a * b);
console.log("Divide:", a / b);

👉 Advanced (User Input)

let num1 = Number(prompt("Enter first number:"));
let num2 = Number(prompt("Enter second number:"));alert("Sum = " + (num1 + num2));

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✅ 2. Temperature Converter

Celsius to Fahrenheit

let c = 30;
let f = (c * 9/5) + 32;console.log("Fahrenheit:", f);

Fahrenheit to Celsius

let f = 86;
let c = (f - 32) * 5/9;console.log("Celsius:", c);

JavaScript has different types of operators used to perform operations on values and variables. Here’s a complete, clean guide 👇

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🔷 1. Arithmetic Operators

Used for mathematical calculations.

Operator	Meaning	Example
+	Addition	5 + 2 = 7
-	Subtraction	5 - 2 = 3
*	Multiplication	5 * 2 = 10
/	Division	5 / 2 = 2.5
%	Modulus (remainder)	5 % 2 = 1
**	Exponentiation	2 ** 3 = 8
++	Increment	x++
--	Decrement	x--

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🔷 2. Assignment Operators

Used to assign values.

Operator	Example	Meaning
=	x = 5	Assign
+=	x += 2	x = x + 2
-=	x -= 2	x = x - 2
*=	x *= 2	x = x * 2
/=	x /= 2	x = x / 2
%=	x %= 2	x = x % 2
**=	x **= 2	x = x ** 2

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🔷 3. Comparison Operators

Used to compare values (result = true/false).

Operator	Example	Result
==	5 == "5"	true ⚠️
===	5 === "5"	false ✅
!=	5 != 3	true
!==	5 !== "5"	true
>	5 > 3	true
<	5 < 3	false
>=	5 >= 5	true
<=	5 <= 3	false

👉 Always prefer === (strict equality)

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🔷 4. Logical Operators

Used with boolean values.

Operator	Meaning	Example
&&	AND	true && false → false
||	OR	`true || false → false
!	NOT	!true → false

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🔷 5. Bitwise Operators

Work on binary numbers.

Operator	Example
&	AND
`	`
^	XOR
~	NOT
<<	Left shift
>>	Right shift

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🔷 6. String Operators

let name = "Aditya" + " Singh";

👉 Output: "Aditya Singh"

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🔷 7. Ternary Operator

Shortcut for if-else.

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

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🔷 8. Type Operators

Operator	Example
typeof	typeof "Hello"
instanceof	obj instanceof Array

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🔷 9. Nullish & Optional Operators (Modern JS)

Operator	Meaning
??	Nullish coalescing
?.	Optional chaining

Example:

let user = null;
console.log(user?.name); // undefined

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🔷 10. Spread & Rest Operators

let arr = [1, 2, 3];
let newArr = [...arr, 4];

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🔷 11. Comma Operator

let x = (1, 2, 3);
console.log(x); // 3