Operators and Loops in JavaScript

🔢 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.

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.

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

• ✅ Use === instead of == to avoid type coercion issues
• ✅ Group logical conditions with parentheses for clarity
• ✅ Avoid unnecessary bitwise operators unless needed
• ✅ Remember string concatenation with + is different from numeric addition

📌 Summary: JavaScript operators

• 🧮 Perform calculations (Arithmetic)
• 🖋 Assign values (Assignment)
• ⚖ Compare values (Comparison)
• 🧠 Combine conditions (Logical)
• 📄 Manipulate strings (String Operators)
• ❓ Make decisions (Ternary)
• 🏷 Check types (Type Operators)
• ⚡ Work with binary values (Bitwise)

🔄 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:

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

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

📌 Example

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

while (condition) {
    // code block
}

📌 Example

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

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

📌 Example

let i = 1;

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

4️⃣ for...in Loop 🏷

Used to loop through object properties.

📌 Example

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

📌 Output

name : John
age : 25
city : Delhi

5️⃣ for...of Loop 📦

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

📌 Example

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

📌 Output

Apple
Banana
Mango

🔄 Loop Control Statements

JavaScript provides ways to control loops.

🔹 break

Stops the loop immediately.

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.

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

📚 Best Practices

• ✅ Avoid infinite loops (make sure conditions will be false at some point).
• ✅ Use for...of for arrays, and for...in for objects.
• ✅ Prefer forEach() for cleaner array iteration when the index is not needed.

📌 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	❌