Logical Operators and Ternary Operator

Logical operators help you make decisions in JavaScript. They are primarily used within if-else statements, loops, and conditional statements where the program must determine what to do next. Learning these operators is important because they improve your logic-building skills, which is very useful for college students and freshers preparing for interviews.

In this chapter, you will learn:

• Logical AND (&&)

• Logical OR (||)

• Logical NOT (!)

• The Ternary Operator (?:)

Let us examine them one by one with clear examples.

Logical AND (&&)

AND returns true only if both conditions are true.

console.log(10 > 5 && 8 > 3);

Output:

true

Example with variables:

let age = 20;
let hasID = true;

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

Output:

true

If any condition is false:

console.log(10 > 5 && 3 > 10);

Output:

false

Logical OR (||)

OR returns true if any one condition is true.

console.log(10 > 20 || 5 > 2);

Output:

true

Example:

let marks = 30;

let passed = marks >= 35 || marks === 30;
console.log(passed);

Output:

true

One condition is true ? final result is true.

If both conditions are false:

console.log(2 > 5 || 3 > 10);

Output:

false

Logical NOT (!)

NOT reverses the value.

console.log(!true);
console.log(!false);

Output:

false
true

Example:

let isLoggedIn = false;

console.log(!isLoggedIn); // true

NOT is useful when you want the opposite value.

Using Logical Operators Together

You can combine multiple conditions:

let age = 22;
let hasCollegeID = true;
let isStudent = true;

let allowEntry = age >= 18 && hasCollegeID && isStudent;

console.log(allowEntry);

Output:

true

All three conditions are true ? final result is true.

Short-Circuit Behavior (Important for Beginners)

Logical operators sometimes stop evaluating early.

AND (&&)

If the first condition is false, JavaScript does not check the second one.

false && console.log("This will not run");

OR (||)

If the first condition is true, JavaScript skips the rest.

true || console.log("This will not run");

This behavior is very useful in real projects.

Ternary Operator (?:)

The ternary operator is a short way to write an if-else condition.
It makes your code cleaner and easier to read.

Syntax:

condition ? valueIfTrue : valueIfFalse

Example 1

let age = 18;

let message = age >= 18 ? "You can vote": "You cannot vote";
console.log(message);

Output:

You can vote

Example 2

let marks = 40;

let result = marks >= 35 ? "Pass": "Fail";

console.log(result);

Output:

Pass

Example 3: Nested Ternary (Avoid if possible)

let score = 85;

let grade = score >= 90 ? "A" :
            score >= 75 ? "B" :
            score >= 50 ? "C" : "D";

console.log(grade);

Output:

B

Although it works, beginners should avoid nested ternary for readability.

Example Program Using Logical and Ternary Operators

let age = 20;
let hasID = true;

let canEnter = age >= 18 && hasID;

let message = canEnter ? "Entry allowed" : "Entry denied";

console.log("Can Enter:", canEnter);
console.log("Message:", message);

Output:

Can Enter: true
Message: Entry allowed

Why Logical and Ternary Operators Are Important

You will use them in:

• if-else conditions

• loops

• form validation

• filtering data

• checking user input

• making calculations

• building apps

These operators form the foundation of control flow in JavaScript.

Practice Tasks (Do It Yourself)

1. Check if a student passed using marks >= 33.

2. Use OR to allow login:

   • If the user enters a username or an email address, allow login.

3. Use NOT to reverse a boolean value.

4. Use ternary to print “Even” or “Odd” for a number.

5. Use ternary to print the grade based on marks.