💻 JavaScript Roadmap 2026 — Part 3

🟢 JavaScript Operators & Expressions

Operators are symbols or keywords that tell JavaScript to perform an operation.

For example:

let a = 10;

let b = 5;

console.log(a + b);

Here, "+" is an operator.

1️⃣ Arithmetic Operators

Arithmetic operators are used for mathematical calculations.

Addition "+"

let a = 10;

let b = 5;

console.log(a + b);

Output:

15

Subtraction "-"

console.log(a - b);

Output:

5

Multiplication *

console.log(a * b);

Output:

50

Division "/"

console.log(a / b);

Output:

2

Remainder "%"

Returns the remainder after division.

console.log(10 % 3);

Output:

1

This is particularly useful for checking whether a number is even or odd.

let number = 10;

console.log(number % 2 === 0);

Output:

true

Exponentiation **

Used for powers.

console.log(2 ** 3);

Output:

8

2️⃣ Assignment Operators

Assignment operators assign values to variables.

Basic assignment

let score = 100;

"=" means "assign this value."

It does not mean mathematical equality.

Addition assignment

let score = 100;

score += 20;

console.log(score);

Output:

120

This is equivalent to:

score = score + 20;

Similarly:

score -= 10;

score *= 2;

score /= 5;

score %= 3;

These are called compound assignment operators.

3️⃣ Increment and Decrement

Increment "++"

let count = 5;

count++;

console.log(count);

Output:

6

Decrement "--"

let count = 5;

count--;

console.log(count);

Output:

4

You'll frequently see these inside loops.

4️⃣ Comparison Operators

Comparison operators compare values and return either:

true

or

false

Greater than ">"

console.log(10 > 5);

Output:

true

Less than "<"

console.log(10 < 5);

Output:

false

Greater than or equal ">="

console.log(10 >= 10);

Output:

true

Less than or equal "<="

console.log(5 <= 10);

Output:

true

5️⃣ Equality Operators

Loose equality "=="

console.log(5 == "5");

Output:

true

JavaScript performs type conversion before comparing.

Strict equality "==="

console.log(5 === "5");

Output:

false

The values look similar, but their types are different:

5 → number

"5" → string

Strict inequality "!=="

console.log(5 !== "5");

Output:

true

Best practice

For normal JavaScript development, prefer:

===

!==

over:

==

!=

because strict comparison avoids unexpected type conversion.

6️⃣ Logical Operators

Logical operators are extremely important when creating conditions.

AND "&&"

Returns true when both conditions are true.

let age = 25;

let hasID = true;

console.log(age >= 18 && hasID);

Output:

true

Both conditions must be true.

Example:

Age ≥ 18 → true

Has ID → true

Result → true

If either condition is false, the overall result is false.

OR "||"

Returns true when at least one condition is true.

let hasEmail = false;

let hasPhone = true;

console.log(hasEmail || hasPhone);

Output:

true

Because one condition is true.

NOT "!"

Reverses a Boolean value.

console.log(!true);

Output:

false

And:

console.log(!false);

Output:

true

Example:

let isLoggedIn = false;

if (!isLoggedIn) {

console.log("Please log in");

}