🔢 Operators in JavaScript

In JavaScript, operators are symbols that perform operations on variables and values.

They are used to manipulate data, perform calculations, and make decisions in programs.

📂 Types of Operators in JavaScript

JavaScript operators can be divided into these main categories:

1️⃣ Arithmetic Operators ➕➖✖➗

Used for mathematical calculations.

Operator Description Example Output
+ 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 let a = 5; a++ 6
-- Decrement let a = 5; a-- 4

2️⃣ Assignment Operators 🖊

Used to assign values to variables.

Operator Example Same As
= x = 5 x = 5
+= x += 5 x = x + 5
-= x -= 5 x = x - 5
*= x *= 5 x = x * 5
/= x /= 5 x = x / 5
%= x %= 5 x = x % 5
**= x **= 3 x = x ** 3

3️⃣ Comparison Operators ⚖

Used to compare values; returns true or false.

Operator Description Example Output
== Equal to (value only) 5 == '5' true
=== Strict equal (value & type) 5 === '5' false
!= Not equal (value only) 5 != '5' false
!== Strict not equal (value & type) 5 !== '5' true
> Greater than 5 > 3 true
< Less than 5 < 3 false
>= Greater than or equal to 5 >= 5 true
<= Less than or equal to 5 <= 4 false

4️⃣ Logical Operators 🧠

Used to combine conditions.

Operator Description Example Output
&& AND – true if both true && false false
|| OR – true if one true || false true
! NOT – reverses value !true false

5️⃣ String Operators 📝

JavaScript uses + for string concatenation.

JavaScript
let first = "Hello";
let last = "World";
console.log(first + " " + last); // Hello World

+= can also be used for appending strings.

6️⃣ Ternary Operator (Conditional) ❓

A shorthand for if...else.

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

7️⃣ Type Operators 🏷

Used for type checking and object handling.

Operator Description Example Output
typeof Returns type of variable typeof "Hello" "string"
instanceof Checks if object is instance of class arr instanceof Array true

8️⃣ Bitwise Operators ⚡

Operate on binary numbers.

Operator Description Example Binary Result
& AND 5 & 1 1 (0101 & 0001)
| OR 5 | 1 5 (0101 | 0001)
^ XOR 5 ^ 1 4
~ NOT ~5 -6
<< Left shift 5 << 1 10
>> Right shift 5 >> 1 2

📚 Best Practices

📌 Summary: JavaScript operators

🔄 Loops in JavaScript

In JavaScript, loops are used to execute a block of code multiple times until a certain condition is met.

They help avoid writing repetitive code.

📜 Why Use Loops?

Instead of writing:

JavaScript
console.log(1);
console.log(2);
console.log(3);
We can write:
javascript
CopyEdit
for (let i = 1; i <= 3; i++) {
    console.log(i);
}

This saves time and makes code shorter & dynamic.

📂 Types of Loops in JavaScript

1️⃣ for Loop

Runs code a specific number of times.

📌 Syntax

JavaScript
for (initialization; condition; increment/decrement) {
    // code block
}

📌 Example

JavaScript
for (let i = 1; i <= 5; i++) {
    console.log(i);
}
// Output: 1 2 3 4 5

2️⃣ while Loop

Runs as long as the condition is true.

📌 Syntax

JavaScript
while (condition) {
    // code block
}

📌 Example

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

3️⃣ do...while Loop

Executes the code block at least once before checking the condition.

📌 Syntax

JavaScript
do {
    // code block
} while (condition);

📌 Example

JavaScript
let i = 1;

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

4️⃣ for...in Loop 🏷

Used to loop through object properties.

📌 Example

JavaScript
let person = {name: "John", age: 25, city: "Delhi"};
for (let key in person) {
    console.log(key, ":", person[key]);
}

📌 Output

Bash
name : John
age : 25
city : Delhi

5️⃣ for...of Loop 📦

Used to loop through iterable objects like arrays, strings, etc.

📌 Example

JavaScript
let fruits = ["Apple", "Banana", "Mango"];
for (let fruit of fruits) {
    console.log(fruit);
}

📌 Output

Bash
Apple
Banana
Mango

🔄 Loop Control Statements

JavaScript provides ways to control loops.

🔹 break

Stops the loop immediately.

JavaScript
for (let i = 1; i <= 10; i++) {
    if (i === 5) break;
    console.log(i);
}
// Output: 1 2 3 4

🔹 continue

Skips the current iteration and moves to the next.

JavaScript
for (let i = 1; i <= 5; i++) {
    if (i === 3) continue;
    console.log(i);
}
// Output: 1 2 4 5

📚 Best Practices

📌 Summary Table of Loops in JavaScript

Loop Type Used For Runs At Least Once?
for Fixed repetitions ❌
while Unknown repetitions ❌
do...while Unknown repetitions ✅
for...in Object properties ❌
for...of Iterable elements ❌